Well, I'm not saying this with any sort of painful longing or regret or whatever, but I can admit that you can always look back on pretty much anything in your life and notice some things you could've done better (if you had more knowledge, or more wisdom, or more experience, or whatever) if you're honest with yourself.
Looking back, if I knew then what I know now, I'd have gotten a degree in 3D Modeling instead of trying to go the freelancing route. That way, I'd be able to be paid 60k - 100k / yr and get health benefits for doing something I've been doing on my own since age 15.
One thing I can say I still struggle with regrets about though...even though I did do the best I could at the time, and even though I don't think it was my fault, I'd have never shutdown my successful freelance work. I was really making more than I ever had in my life back then, I was stable, I was doing well, and I was enjoying it. I was making more than I am now as a full time employee earning on the high end of what undergrads are able to earn. That was when everything went wrong for me.
Then again, I wouldn't have some of the relationships I have today, as my struggles throughout the years brought us closer. I might've gone undiagnosed and still going through episodes without knowing it. I wouldn't have developed some of the character I developed because of those difficult times. So...I don't know.