Well, I can only speak from personal experience, but my only regrets are that I spent too much time on BS and not enough on life when I was younger--and this comes from a person that spent very little time on BS! My view is that people who are going to succeed in life are people who are going to succeed in life.
As a note on marriage, I think a lot of divorce depends on the circles in which you run. We're (my wife and I) thirty-somethings, and in our circle, we don't know anyone who is divorced. Divorces are disproportionately skewed towards the lower class. Keep out of it and you're much, much less likely to divorce. For my own marriage story, I met my wife while I was in graduate school. I attended a good graduate school, but I got in by virtue of very good test scores. I wasn't particularly interested in college, and my grades reflected that lack of interest. If I applied myself in college, maybe I would have attended a better graduate school--but then I wouldn't have met my wife or had my daugher.
Scary to think of the road not traveled.
I agree completely with you about divorce and the circle of people you associate yourself with. I too don’t know anyone in my circle of friends who has had a divorce, and I am in my mid 40’s. Nearly everyone we know has been married 15-20 years, has 4 to 5 kids, went to college and most of them graduate school and nearly all of them are doing very well financially.