Can someone please explain why I do this?

You are really worried about getting hurt SO if you keep it up long enough you will never be loved. You will chase them all away. Sure can't get hurt that way, can you? Do you not think that guys worry about getting hurt too? Sure they do. Take a chance and see what happens. If you don't like him, let him go. If he gets hurt, he will have to deal with it. The same is true for you. Tell yourself that you could never love someone who did not love you back so you refuse to be devastated. Remember , it may work out wonderful..It is better to have loved and lost than never to have loved at all.