To the person who pushes everyone and everything away,
I understand. I have been this person a few times, and I'm still working on it. When relationships or friendships become complicated, you push people away. You don't want to deal with it; instead, you try to avoid confrontation. Even when you find a school assignment too difficult, you procrastinate and only work on it when you actually need it completed. I've been in similar shoes.
You may be pushing someone away because you are irritated by them, angry at them, or just tired of dealing with a person who just doesn't treat you with respect. In those cases, it may truly be the right thing to do. But give them a reason. Don't do it without an explanation, or else how will they ever learn?
More importantly, stop pushing people away when you're scared. Sometimes you push away those who challenge you in a positive way, but that's what all of us need. Don't limit your friends to a certain group, and be open to meeting people who are different from you. These people can make an enormous impact on you or give you opportunities to participate in something you never thought you could do.
I had a friend who was mostly only close with her friends from dance, but was then introduced to theatre by an acquaintance. She looked forward to the first theatre club meeting but had no idea how much it would change her life. Because she reached out to new people instead of pushing away these people and the theatre crew, she participated in an act (literally) that she quickly fell in love. Now she's in her first year at university and plans to major in drama and the arts.
Even if your experience with trying something new is not as successful as hers, it is never wrong to expose yourself to new things. No one really knows what they are capable of, or what they are passionate about, until they put themselves out there and try.
Create a new outlook on the situation: You are brave enough to handle whatever or whoever it is you are nervous or scared around. You can face it, and you will. The easy route won't help you grow and learn; the more challenging path will present obstacles that you will someday overcome.