I have an addictive personality, which means I like doing everything too much: coding, writing, visiting interesting web sites, smoking, drinking, eating. Basically if it has any sort of positive feedback loop at all, I can make a bad habit out of it.
Fortunately I began suspecting this early in life, so I didn't end up a coke-head or worse. Instead I've learned to balance all of my bad habits in a way that continues to optimize productivity for me. So for example after smoking for five years in my early 20s, I quit cold turkey. As for eating, I'm learning to control my blood sugar levels. I'm finding there is a blood-sugar/caffeine/alcohol feedback system that I'm dismantling. But then there are big problems that I'm still working on, like procrastination and too much web reading (which are related!) I probably lose dozens of hours a week on these. Sometimes I make progress, such as no TV (except for movies) Still others seem intractable, like enjoying coding so much I keep over-coding things.
I think as you get older you begin to realize how screwed up you are -- if you are introspective at all, that is. Some folks aren't introspective at all, or if they are they aren't able to critically see what needs fixing. These are the ones to be pitied. But introspection always has kind of a sad quality to it. I know for me it was a lot more fun when I used to think I was bullet-proof.