Maybe that's your problem. You're so confident in yourself that you just expect things to happen for you. (That's what my problem was)
1) "I would be in competition with others who've been practicing their trade for many years."
Common dude that's just BULLSHIT. What do you think college students go through?! They enter a market without any experience, competing with people who are well established and experienced. That's what people do, that's what companies do. The Google guys starting working on a search engine in an era when Microsoft, Yahoo, Lycos, & Alta Vista were established competitors. Same with Facebook > Myspace, same with Walmart > K-Mart > Sears Roebuck, with MS Word > Word Perfect, and the list goes on and on. A bunch of inexperienced no-bodies little by little outrun an experienced established player. Statistically & Historically speaking, you have a chance. So get that "I can't compete" argument out of your head. THAT is what's holding you back.
2) There's "problems" and then there's "issues". Problems can be solved. Issues can never be solved, they must be adjusted to. A flat tire is a problem, a hatred of men because of experiences with your father is an issue. And just like losing your legs, not having a childhood, and jealousy due to insecurity, your "deep seeded regret" is an issue. You cannot fix it. You can only normalize to it, understand it, and move on from it.
3) Cognitive behavioral therapy, as others have mentioned is REALLY amazing and works very well for issues. I got over body dismorphic disorder using CBT. You can't change the world to make yourself feel better, you can only change yourself, your point of view and way of thinking and that's basically what CBT is. CBT can be done with a therapist to talk you through learning to recognize and later stopping the thoughts that lead to your regret. Or you can learn about CBT methods and do it yourself like I did. (I talk to myself 6-12 hours a day which is why I went the self-mediate route. Therapists took too long and were too expensive.)
4) Learn that there is a dark side to dreaming, wishing, fantasizing, and desiring. A very dark side that leads to nothing but disappointments and regrets of not having reached the dream, wish, fantasy, or desire. We've been conditioned our whole lives to dream big and keep trying but when you don't reach those dreams you've set yourself up for decades of regret and heartache. You need to stop comparing what you have to what you wish you had, and instead compare what you have with what others do not. You're lucky, realize that.