1. We sometimes go against our willingness to do something merely to make friends happy. Violate is a strong word. "Go against" is more general. Also, violate does not need against. 2. Actually, when faced with peer pressure, we should learn how to insist on our own principles. "Peer pressure " is a commonly used phrase in English. "The pressure of peers" is not grammatically incorrect, but is sounds strange because "Peer pressure" is so common.