I think the regrets are what really keeps me from using. I don't want to go back to where I was, I don't want to get that bad again. It's not the blown money or actually using that I regret, or even the close calls where I almost got arrested for buying dope or driving drunk or whatever. I don't want to hurt more people, or myself. Those regrets, or lessons if you prefer, were my original motivation to quit.
Even with all the trouble involved I can't say I 100% regret all the drinking and drugs. I had a decent amount of fun with it before it became more trouble than it was worth, and it kept a few demons at bay until I was ready to deal with them (although by that time there were a lot more demons to deal with). I also gained a certain amount of compassion that I never had before. And it changed how I view the world in almost every facet of my life. It wasn't all bad, it just became more trouble than it was worth.