Also edited to add: just wanted to clarify that I don't want to be construed as harshing anyone's mellow, or whatever. But what I'm saying *is* the truth.
And FWIW, I very much enjoyed my partying lifestyle, too. Socializing, drinking, and food have been very, very big parts of my life. Drinking in particular I was very good at for quite a long time. I didn't choose the lifestyle I have now because I am a natural Puritan and enjoy spending nearly all of my disposable income on my health instead of on the finer things in life. I chose the lifestyle I have now because I figured out if you don't feel good mentally and physically, pretty much nothing else matters, and even if you can't entirely achieve perfect health and well-being, it's definitely worth striving for.
Good news is that if you can reconstruct your health, you may be able to back to a moderate version of what you could get away with in your 20's. As I said, I can take a drink now and then with no ill effects, even though I find I just don't really want to any more. I've found I enjoy leaving my methylgroups and adrenal function intact more than I like alcohol. Feeling healthy and sleeping well becomes addicitve, too. And it's perfectly possible to truly enjoy being around people to socialize without indulging in more than a bite or a sip or two of whatever's on the table, just for the taste. It's usually the whole glass or two of wine or beer, or the whole piece or two of cake or pie that causes the problem, not a couple of bites. One strategy that helps with this is to eat a big healthy meal before you go out.
Bad news is that if you reconstruct your health, get cocky, and go on a big dumb old person's binge, you can undo almost all your hard work and have to start all over again. I've done that, too. Did it a couple of years ago, in fact. I had worked very hard on my health for over a year, lost 40lbs, looked great, and felt even better. I had basically restored my adrenals. Felt like I was in my 30's again, if not my 20's. It was that good.
Then one of my oldest friends had her 50th birthday party. A lot of fun people showed up that I hadn't seen in a very long time. We partied like it was 1983 all over again. Party started at noon on Saturday, and we all crashed at about 6a Sunday morning. That little episode set me back so far that I still haven't entirely recovered from it, and it's been over two years. I was actually pretty okay in the couple days immediately after the party, and I even congratulated myself on escaping without the big hangover. But then in subsequent weeks it became abundantly clear that I'd really done some damage to myself again. Energy went down, exercise tolerance disappeared again, depression returned, sleep patterns disrupted, junk food cravings came back, etc. I didn't go entirely back to square one, but I was close enough to kiss it. Call it square three, which was bad enough.
Point being, I guess, is we all just have to decide which opportunity cost we're willing to pay. Good health is definitely the scarcer, more valuable commodity.