Final installment of “Harry Potter Diet” series.

I’ve taken a few weeks off writing about The Harry Potter Diet. There are two reasons.

1. It was wildly more successful than I could have ever hoped.

2. Now comes the hard part.

OK, one part at a time. So, many of you might remember that back in May, I bought a Harry Potter button-down shirt to impress my daughters. There’s a great Seinfeld line about how all dads dress in the style of the last good year of their lives. I certainly do, that year being probably 1993, which means that I NEVER wear a short-sleeve button-down shirt, wouldn’t know how to wear one, couldn’t pull one off.

But all dads would like to, every now and again, surprise their daughters.

So I got the Harry Potter shirt. XXL.

It didn’t fit.

It didn’t really come CLOSE to fitting, if I’m being honest. I could barely button the buttons. And that was, for me, like looking directly into the not-yet-dimmed sun. Many years ago, I readily accepted my fate of wearing XL clothes. (I like oversized shirts, I told myself.) That didn’t even seem like a big deal to me — XL is fairly cool.

I was less ready to accept my entrance into the XXL club, but … I didn’t take it too badly. It was better than the alternative, which was changing my life. I filled my closet with XXL shirts and size 42 pants and told myself it was OK. I took the blood pressure and cholesterol medicine and told myself it was OK. I went through various periods of time where I lost some weight, sometimes even lost quite a bit of weight, but it never lasted very long, and I honestly didn’t think that much about it.

But something snapped in my brain when that Harry Potter shirt didn’t fit. The idea of living an XXXL life … it was haunting and dismal and more than a little bit frightening.

It’s hard to lie to yourself when the XXL shirt doesn’t fit.

So I went on the Harry Potter Diet, with the immediate and powerful goal of being about to wear that stupid, pointless and wonderful shirt. And, I’ll give away the ending here: I still can’t wear it. But now I can’t wear it because it’s way too big.

People have often asked me during this Harry Potter Diet process, “What have you been doing?” I’m sympathetic to the question; it’s the same question that I’ve asked weight-losers countless times over decades.

But the reality is that it’s not exactly the right question. That’s because I’m just doing what I KNEW I had to do. I know no secrets. I've come up with no scientific breakthrough. I've done three things (well, 3 1/2 — you’ll see) and they're the three things that EVERYBODY knows you have to do if you want to lose weight:

1. I cut Diet Coke entirely out of my life. This was a hard and painful thing to do, and I miss it terribly. But this was for me the critical step for a couple of reasons, the first being that (as doctors had been telling me for years) Diet Coke can create hunger cravings. I don’t know that it does that for everyone, but it sure as heck did for me. The second reason is probably even more important: In all my previous diet attempts, I’d continued to drink Diet Coke (after all, DIET is in the title). I needed to stop drinking Diet Coke as a symbolic gesture as much as anything else, to prove to myself that this time was different. I had headaches for a week. Anytime I eat anything salty I see Diet Cokes in my daydreams. But I did it.

2. I mostly stopped eating all those things that everybody knows you have to stop eating to lose weight — bread, pasta, desserts, french fries, pasta, red meat, pizza, fried foods, pasta and, did I mention pasta? Yeah, it was the pasta that was the crusher for me. I so love pasta.

3. I cut down portions. This, it turns out, was not as difficult as I thought it would be, in part because by cutting down portions I was able to cheat sometimes.

I have a story on this one. One day, after something really good had happened (it might have been when I sent in the final version of The Life and Afterlife of Harry Houdini … did I mention I wrote a book about Houdini that's coming out October 2019?) we went into a Cold Stone Creamery as a family, and I said: “I’m going to celebrate and eat some ice cream.” It had been at least a couple of months since I’d eaten anything like ice cream.

I went to the counter to order and noticed that at Cold Stone Creamery they have the calories listed — the range was something like 240 to 10,394,832 calories.

“Hey,” I said, “what can I get that’s 240 calories?”

And the guy pulled out what can I only describe as a comically small cup. It was exactly the kind of ice cream cup you would pull out on a sitcom when some dad asked, “What can I get that’s 240 calories?” It was the cup that you use to measure how much Robitussin you should take.

I shrugged and ordered a Robitussin cup of chocolate ice cream, and you know what? You won’t believe this, but … it was WONDERFUL. I mean, yes, of course, I could have eaten more. But I’ve started believing deeply in the 95% theory of joy that my friend Dan has come up with. Dan is a car guy, and he says that a Mazda Miata gives you 95% of the experience that, say, a Porsche or some similarly awesome car will give you. For a real car guy, that 5% difference is everything, but for the rest of us, hey, we might never be able to get a Porsche, but someday when the kids are out of school, who knows, maybe you can get a Miata for like one-third or one-quarter of the price. And that would get you 95% of the way there.

Having that little cup of chocolate ice cream got me 95% of the way there — for like one-third or one-quarter the calories. It was delicious and filled my desperate desire for something sweet, and it didn’t hurt much at all. I will tell you that it surprised me as much as anything.

So I mentioned there was a half-thing I’ve done … it ends up being the most interesting thing, because it’s sort of trendy and slightly unexpected, but I suspect it’s also the least important thing. But I’ll tell you — most days I do that windowing thing where I do all my eating in an eight-hour window. Again, I don’t know if this has played any role in the weight loss (I’m skeptical) but it fits my life, and it's something to say when people ask, “What have you been doing?”

After about a month of going on the Harry Potter Diet, the shirt fit. It was a touch snug, but it fit. After two months, it fit comfortably. After three months, it was loose. And after four months, it was kind of absurdly loose. I was no longer an XXL. I had moved back into the XL neighborhood.

After five months, the XL shirts started feeling too loose.

Let me share this experience I had a couple of weeks ago — and I don’t know if this will mean anything at all to you, but it was SO crazy to me. Nothing in my closet fit anymore, so I went to the store to buy some shirts and jeans. And if you have ever lost a lot of weight, maybe this will ring true to you: I was scared to death to try on the regular old large shirts. Scared … to … death. I can’t fully describe this feeling; my brain told me, “You know what, I’ll bet those L shirts will fit me now.”

And my heart told me, “Hey fatso, it will be embarrassing. Just buy the XL shirts and be grateful for how far you’ve come.”

So I did what I have almost never done: I went to the dressing room and tried on the clothes. But it was more than that: I brought in two versions of each shirt. I brought in an XL and an L. And each time, I tried on the XL first.

And I said to myself, with surprise each and every time, “You know what, this feels loose.”

Then I tried on the L, and it fit, and I would look in the mirror in pure shock.

Then I did the same thing with the next shirt. And the next. And the next. Each time, before I tried on the large shirt, I felt that same wave of terror, like this wasn’t real, like I was a fraud for even trying on an L shirt. I haven't been an L since I was in my 20s. And each time the XL shirt was just a little loose, and the L shirt fit, I wanted to laugh, and I wanted to cry.

A 51-year-old person should not feel so emotional about shirt sizes.

When people have lost a lot of weight, as you well know, the two questions are, “How did you do it?” usually preceded by “How many pounds have you lost?” I can tell you that I’ve lost 52 pounds. That’s good, right? But I feel no emotion about that number. I feel tremendous emotion about dropping six inches on my jeans size and about dropping from XXL to L and about being able to go through fairly intense tennis drills without vomiting (that’s not a fun story) and about how good it feels to go on two- or three-mile walk-jogs without feeling like I might collapse into a puddle of sadness.

So, I mentioned the hard part …

I reached my goal. I passed my goal. I crushed my goal. Along the way, of course, I created a new goal, and then another new goal, and another. But here’s the thing: The new goals are not as compelling as the old ones. The shirt fit. I dropped sizes. My doctor took me off those medications. And now the goals feel, I don’t know, contrived. There’s a weight goal I’d like to hit. There’s my college weight, which doesn’t feel impossible to reach. There’s the possibility of a shirt with an M on it.

But none of those goals feel as real, as immediate, as important, as vital.

I have a sports analogy: The urgency has changed. This is when teams go into prevent defenses. This is when teams stop being aggressive in free agency. This is when the temptation is there to stop innovating, stop taking chances, stop looking forward and instead start looking a little bit backward. And I feel myself slipping a little. Not a lot. But hey, a little pizza won’t hurt me. A little pasta won’t hurt me. Hey, why not have a piece of cake? I mean, I’ve got this.

So far, I haven’t seen a slide — I do weigh myself all the time to check. But I also have seen the momentum stop. And I’m a little bit worried about that. I need another goal that inspires me as much as the Harry Potter Shirt did. And winter is coming.

I think that’s the secret, really. You hear people say that losing weight is easy on this diet or that, but it isn’t easy. You hear people also say that losing weight is impossible for this reason or that, but it isn’t impossible, either. I think it can feel easy or feel impossible because it’s somewhere between those two poles, and I believe that what matters most is not the diet, not the method, but the reason. It can be a profound reason — you want to live longer. It can be a more specific reason — you want to fit into a two-piece this summer. It can be a thoughtful reason, a silly reason, a selfish reason, a reason that wouldn’t make sense to anybody else in the world.

But that’s the thing: The reason itself doesn’t matter … except to you. The only thing that matters is that the reason moves you completely. And as far as finding that reason, that thing that will make you change your life, well, I don’t know anything about anything. But I will say that sometimes it’s the dumbest thing in the world. I had doctors tell me that I had to lose weight. I had family members tell me that I had to lose weight. I understood the stakes, knew the risks, and none of that ever inspired me to really and truly change.

Then I bought that Harry Potter shirt at Target.

I have to say: Best $19.99 I ever spent.