Being Used?

Have you ever had a fear of being used by the one you care about? Well I know I've been used once or twice but this is the first time It hurt so bad...I'm not going to get in details. Why do people have to be so crule to use people and just not care? I don't undertand I can't just use people cause I still go by the saying "Don't do to Others what you don't want done to you" and I live heavily by that. But anyways Using people is wrong and I hope anyone that reads this doesn't do stuff like that.