I wasn't even a train wreck, I only drank a couple times a week and usually not more than 5 drinks. But there are so many little effects, and as I improved the rest of my life, I realized it just wasn't worth it anymore.
When I drink I say dumb shit, revealing things I don't really want people to know. Once someone hears that stuff, they're relegated to a certain type of friend. Then I have to keep straight who knows my secret shit and who doesn't.
When I drink I stay up late, I'm tired the whole next day and even the day after. I'm really sensitive to lack of sleep. So I don't get as much done and I waste the whole weekend. If you do this most weekends it totally gets in the way of moving your life forward. You don't have time or energy for the stuff you think you want.
I get really hungover REALLY easily. I always think it's worth it, but the next day I just don't fucking understand. It's not just headache and queasy, I mean intense migraine and vomiting for hours and hours. How is that worth it? The next day I'm shit too, it's like recovering from the flu. How is that fun for me.
I used to be bored and have a lot of free time, so I drank. I felt unsettled and unfulfilled in general. Bit by bit, I added more things to my life, and slowly found that I literally didn't have time to wast 2 nights/wk + 1-2 days recovering, I mean that's more than half the week.
Most importantly I got my mental health together. I'm in therapy and trying to make good choices, because I feel better about myself and I like my life more. I'm on a mood stabilizer that interacts really badly with alcohol. More importantly, I can now make progress toward my goals and not come crashing down right after. (Made progress during a mania then ruined everything in the depression that inevitably followed. Or, made slow progress while stable, then followed unbelievably stupid impulses while manic.) I'm not self-destructive by nature anymore, it's a choice. I hated myself every time, so why keep choosing it? I am pretty good at life now, so why would I want to fuck that up on a regular basis?
Yeah being drunk is really fucking fun. But I like my life and I like myself. I still have a ton of fun, in fact I do a lot more interesting things instead of defaulting to booze. Also, when I want to feel drunk-ish or hang out with drinkers, I turn to weed - no hangover (and no calories either). Everything is better.
tldr: Awful hangovers, medication interaction, tired of stupidity, done with self-destruction, want more out of life, smoke weed, happiness