Maybe it's already happened to you. But there are some things you can do to make that roommate relationship tolerable-even fun. So many times, roommates fail to express what they like or dislike. When people whine or gripe, they're usually not interested in solving the problem. They just want to advertise their unhappiness.
Some people have trouble lending out stuff at all, so be sensitive.
There's a difference between sharing excitement and bragging. However, a roommate that brags is annoying to everyone. It's okay to share your opinions. But don't assume that you know what's best for your roommate. A relationship break-up, a fight, a bad grade, many things can cause emotions to flare.