Someone betrays your trust. A jerk cuts you off on the road. Your child disobeys you and breaks your “house” rules. A business partner cheats you. A friend says something behind your back that is hurtful. A co-worker takes credit for your work. A boss puts you down or takes away hard-earned benefits.
Obviously, the reasons why you might become angry are many. In fact, there are likely hundreds of reasons—big and small—why you might become hot under the collar during a single day. That said, the issue is not if you will become upset—but how you will deal with it when you do, and the impact it will have if you don't deal with it effectively.