The worst decision I have ever made was indecision. I either made a mistake and learned from it, or did something right and was proud.
I can only offer the advice that my more outgoing side always offers me: "Fuck it"
Shit happens. The sun will still rise in the morning. Don't be afraid of mistakes, be afraid of never getting a second chance. Throw caution to the wind and never look back. The past happened, we're just going to have to live and learn from it.
Go talk to her; go give him a chance. Don't be afraid of who you are. We don't need their approval to be happy