it is because we are too nice to them while putting ourselves in the difficult situation. In that way, we may build up the resentment. Sooner or later, this resentment will come out, then in that case, we will all think we are victims.
Try to be VERY nice to ourselves, and be straight forward to people but not rude. If they are really our friends, they will understand, and they will come back in a good manner. Most of them do mean to hurt us or take advantage of us.
Good luck, and be happy