I'm jealous of people who can drink normally, too. But I'm also jealous of lots of other things... people who've read more than me, people who speak other languages really well, people who are super fit, people who are all outdoorsy and know how to backpack in the woods properly, people with really healthy relationships, etc etc...
Of all the things that I wish I could do, alcohol's the only one I know I can't do. I spent years and years trying and it didn't do me any good. So now I figure if I put in even a bit of the effort I did towards that goal into those other things I'm jealous of, my life is going to start looking pretty awesome.
Hang in there and try to focus on the amazing things that better physical and mental health will make possible, not just the sacrifices you need to make to get there. It sucks, I know... I winced when I read what you wrote about swimming and then drinking beer, because that sounds like a perfect day to me. But the cost is too much, so I try to focus on all the other ways a day could be perfect.