None. I'm at a stage in my life that I'd be sad if I missed (I'm 39, btw) what I've done. My job sucks, I'm barely scraping by money wise, but my life experiences have been wonderful.
Restarting my adulthood would mean ultimately making different decisions. I'm happy with my choices up until now.
I wrote a horror novel, called "Spare Parts." A whole damn novel! You can check it out, and other free short stories at http://www.aarondeck.com