What should you do if you are in love with a good friend who is in a relationship?

The best thing you can do is still remain friends and keep your feelings to yourself for now. You may get a chance if this person decides to split-up and if this is the case then don't wait so long to tell them how you feel. By butting in now it will only cause hard feelings and you'll end up the loser and ruin any chances you may have. I know it's hard, but waiting sometimes pays off. Good luck Marcy