WARNING: I will smite you like an almighty smiter if you wake me up before my alarm goes off
I would have to say the most important life lesson I've learned, is that there's far more to life than going to the pub every weekend. I barely go any more, but at one point I was religious about it.
I kept seeing the same faces, having the same conversations, drinking the same drinks and going straight back to work on Monday with a hangover and a large chunk of money missing from my bank account.
I've found a lot better things to fill my time up with now and I actually feel happier for having a break from alcohol. I had no idea that I would become more productive by not going out.
Might seem like a simple thing to most people, but I certainly don't miss listening to people fight in the street any more either lol.