Regrets is making decisions in the past. When you dont approach you go home and try to change your behavior in the past, but you cannot and you suffer from it. Make decisions in the present. If you made decision not to approach a girl, this is the decision you made and nothing you can do about it anymore. I bet it was your best choice at the moment when you were making this decision. All you can do is to prepare your self for future decisions, do not regret not approaching a girl, simply decide you gonna approach next time, and plan what you gonna do. Not to regret is easier said than done, it is not so easy not to think a though that is stuck in your head. But there is a trick for it - since you just can't think 2 thoughts at the same time, you need to replace one thought with another, preferably with something that you like, something that motivates you, something that makes you feel successful - it can be a memory of a good time, or even a fantasy, you can watch a movie - you got the idea? There is even more powerful thing than replacing the negative thought with another thought - talking to someone else, with your friends, your relatives, teachers, random people on the street, supermarket, anywhere. Talking about anything positive. When you talk - you are present and cannot drown in your regrets.
This is how you beat your regrets and think how you improve in the future.
Approaching hot girls that you are attracted to is nice and cool, but if you are nervous and they weird out, I might develop a bigger fear and not approach them in the future.
I recommend you start approaching someone who you don't necessarily like, or not attracted to. Start any conversation, socially acceptable. Like ask for directions, time, use any kind of opinion opener (there are many of them on the internet). Have no agenda, dont ask for the phone numbers or anything. You may say a compliment, but dont expect anything in return. If you dont feel really comfortable talking with girls, talk with guys first.
You will notice that slowly you will be shifting to a more social and talkative mode. Start talking to guys, then social topics with unattractive girls, then attractive girls, then flirting. Remember the state. Unfortunately every night when we sleep our nervous system slows down and every morning it is very slow and we dont want to talk with anyone, every day we need to speed up our brains to get into the social mode, where we can easily talk with anyone. That is why when you are there remember the state and use some kind of Anchor to help yourself get into this state faster in the future.
One more thing, in your language use more or if possible only positive words and statements.