You're experiencing what Seth Godin calls "The Dip" - There has to be some hardship endured before you come out looking good on the other side. You really are being way too hard on yourself. If you were mature enough to take a risk at the age of 20 then it shows you're well on your way to hedge other bets in life for the long term. That's a very good mark of a successful person. Only thing is, you're giving up a little soon. Dont let things wear you down.
Success takes time.
Wish you well ;-)
PS. Just for the purposes of consolation. I went through something similar at your age. Im now 30 and while i dont feel as suffocated as i used to, i know exactly how you feel. It does get better. I assure you. I dont regret (for the large part) the decision that i made. I just wish i had had the courage to be even bolder with my choices, and sooner.
"The Dip" does seem to exist. The worst and most painful part of the long distance race is at its end but if you get through that, you feel much better. And in the end you are better after the race than before it, in all terms.
Success takes time.
Wish you well ;-)
PS. Just for the purposes of consolation. I went through something similar at your age. Im now 30 and while i dont feel as suffocated as i used to, i know exactly how you feel. It does get better. I assure you. I dont regret (for the large part) the decision that i made. I just wish i had had the courage to be even bolder with my choices, and sooner.