@atamarashi:
Everybody has something that follows them to the present. Your friend is right. You shouldn't dwell on the past. It's hard to forget everything about the past. Like I said, everybody has something that haunts them each and everyday until the present. May it be something stupid that they did in the past, to something really embarrassing, to something traumatic that happened to them. Everything is hard to forget. Recently, I've also been struggling with the same problem. There's always a certain memory haunting me until I couldn't go to sleep at night. My older brother used to always tell me this when I was little, "whenever you're sad, or scared about something about the past, all you have to do is overwrite them with happy things. It may take time, but as those happy times build up, they make you forget your sad times." That's something that I still live by today.
Remember that it's good to analyse things, but you should only analyse to a certain extent. You shouldn't over-think to the point when you start to become afraid of it. Mainly because it's bad for your mentality because you start to become paranoid of everything.
Live in the moment. Live each day to it's full content. If you make mistakes, learn from them. Focus more on the positive than on the negative. That way, you'll be able to overwrite your fears.
@milena:
First of all, we're the same age!
I know the feeling of moving to a new school, where you don't know anybody. In each school, there are the main groups, but then there are also the "in-between" groups. But instead of worrying about which group you're going to be in, focus on yourself. Do you know who you are yet? When you're at school, you should be yourself. You don't have to apply tonnes and tonnes of make-up because all the girls are doing it, or act in inappropriate manner so you'll be accepted into some group. All you have to do is be yourself, and people will respect you for that. Also, there's bound to be at least one person in your class who will like you for who you are.
As for the girl you mentioned, talk to her more! If you want to be her friend, go for it! Get to know her better and then learn more about her friends! they might not be completely absorbed into make-up and acting like they rule the world. Looks can be deceiving, and the best way to get to know a person is to talk to them.
Best of luck!