Friend of mine from college was quite the partier growing up. I'm talking underage trips to Tijuana, $30k in debt while still in high school, how-does-he-not-have-herpes kind of partier. Grew up under the influence of his father who used to throw parties that ENTIRE BIKER GANGS would crash (for all the biker gang members out there who are excited to call me out on relating third-hand hyperbole: I think free booze, live music, and readily available drugs had a lot to do with the type of people these parties would attract).

He met a girl (25 y/o, religious, good job, virgin... seems like it matters) and had what was probably the first long-term relationship of his life. He still liked to get black out drunk and throw epic parties mind you, but he was committed to her from the moment they met onwards.

Graduation comes and goes and they decide to get married. We have a great stag night, the wedding is a blast, everything seems normal-normal. In retrospect, the marriage itself was a turning point for him, but it was subtle. A few moths later he and I are in the same city in which we enjoyed his pre-wedding night of debauchery and we decide to re-live said night. He doesn't fare so well (blacked out, hugging the sidewalk) and I call for pick up. His wife shows up; panicked, upset, out of her mind. She tells me if this is the type of man he is going to be, the type who will risk his family and career for alcohol, she doesn't want any part of it. Says she will divorce him if it comes to it. doesn't want to have children with someone like this. The next morning we come to and are summarily kicked out of the house.

I don't know what was said between them, but several years down the road and he has never been the same. Very much the straight-and-narrow type nowadays, he still likes the occasional beer session, but never out in town and never around his wife. Whatever ultimatum was passed when he had his wits about him the next day, it stuck.

TL;DR: Partier chose his wife over his former life.