Set ground rules in writing. Harlan Cohen suggests in his book "The Naked Roommate" to make it clear that you want to get along. Make a roommate contract and set up weekly meetings so that you can voice any concerns. Respectfully help your roommate be aware of what he's doing to bug you, because he might not realize it. Lsten to your roommate in case you do something that bothers him.
Be kind and stay calm. The American Psychological Association's article entitled "Controlling Anger Before it Controls You" advises you to slow down and think through what you say during a heated discussion. Be sure to listen to your roommate as well, and don't jump to conclusions. Offer to compromise, because if you are willing to make sacrifices, your roommate will most likely follow.
Stand up for yourself. For instance, if your roommate steals your food, keep close track of what he takes, and call him out on it. Linda Fiore explains in her book, "The College Roommate from Hell" that most everyone living with a roommate has a conflict or two at some point. Fiore says that many of these conflicts can be solved with an immediate conversation, rather than assuming they will eventually fix themselves.
Spend time in other places and with other people. If you and your roommate truly can't get along, find different places to relax. Living in cramped quarters with someone you don't like can be more tolerable if you're not together all the time. According to "The Naked Roommate," living together is not about being best friends, it's about getting along well enough to exist comfortably.
Avoid branding your roommate as "insane." Personality and cultural differences can cause roommates to fight, but they are fixable. If your roommate actually has a mental problem, she needs support rather than judgment. In "My Roommate is Driving Me Crazy!," Susan Fee notes that depression, anxiety, eating disorders, substance abuse, and self-injury are all common health issues that frequently go unnoticed and undiagnosed. If you think your roommate has one of these conditions, urge her to seek professional help.
Leave. If living with your roommate has become unbearable, request a change. Explain your problem to your Resident Adviser or landlord. Fiore explains in her book that while living with a roommate is similar to being in a marriage or relationship, you do have the ability to make a clean break without spousal or child-support payments if things get unbearable.