Don't tell people how they should feel.

People have all different life experiences and all types of views.  Once I was telling a group of friends that my daughter had started dating a boy with a disease that he could live with, but it would greatly impact his lifestyle, thus impacting hers if she got involved with him.  I voiced my concern with these friends and one of them said, "You shouldn't feel that way".  Who was she to tell me how I should feel?  I hate that saying.  When you say that, you are judging that person.  What you are saying, is that YOU know the right way to "feel" and the other person is "wrong".  So try to understand where the other person is coming from.  Offer up alternatives, or voice how you might feel in the same situation, but unless you have lived the exact same experience, don't tell someone, "you shouldn't feel that way".