I might look back and regret some things, like wishing I'd spent more time with my kids while they were growing up. But then too I don't know any parent that I'm friends with who doesn't have similar regrets.
I make it a point to look forward, not backward, with most other things. I have a great wife, two wonderful kids, and I live a comfortable life. Not much else to regret really. I've definitely been blessed. Compared to a lot of people, I'm living a dream life.
Hard for me to be anything other than grateful for the life I live, the family I have, and the friends who've made my life infinitely sweeter.