I absolutely believe that running saved me from becoming a really f'd up person. I was diagnosed as bipolar when I was in highschool. I didn't believe the diagnosis and refused meds. I went out for track about a month later and it pretty much changed my life. Now out of college, I still use running and frequent exercise as an "outlet" and to keep me "normal." I think I still have minor manic phases with periods of depression, but the swings are far less dramatic and I'm able to keep it together in regular life.
I also probably have a very type-A personality, but only when it comes to things that I care about. In other words, once I latch on to something I'm compulsive about it to the point where it consumes me. This was very effective for training and still is. It has helped me tremendously in the working world, but only because I am at a job and in a career field that interests me.
In college (and highschool) my grades showed massive fluctuations in which subjects I cared about vs. those that I didn't (like A's vs. D's). Overall I'm pretty happy with the person I've become most of the time, but I'm in constant need of finding difficult goals to reach, otherwise I spiral into deep depression and heavy drinking.
I will say that I had my best races in college on the manic upswings. I would basically have 4days-2weeks of absolute awesomeness, in training and just in life in general, followed by 2-4weeks of feeling down and lethargic. Hard to control, but made for some awesome races and great memories.