When we think of angry people, optimistic is most likely the last thing to come to mind. Yet, I can assure you that beneath the spiky surface, they are very optimistic even though this is actually making their lives harder.
Imagine a character: James
James has been married fifteen years and has told his wife on various occasions not to interrupt him while he is reading his newspaper. His wife finds this very annoying, so she decides to ask him when he is planning on preparing dinner. This makes James very mad, and he starts shouting and screaming like a madman.
James is hopeful. He has an unwavering faith in a world in which his partner will always understand him. This hope that James has and many others like it are unrealistic, and when they fail like they are supposed to, he screams.
James, no matter how hard he tries, will never remove frustrations from his life. But if he truly tries, he could maybe change what these frustrations mean to him. He could learn to accept reality as the sad truth it really is. That life, not including the brief moments of happiness, is a series of griefs, disappointments, frustrations, and catastrophes. From this, James could learn to get less angry.
In many ways, most of us are like James. Not because we are constantly angry, but because we get constantly frustrated at the sudden defeat of our expectations. In order to not get frustrated at every single disappointment, we must get a lot less optimistic about how life will go. In other words, we must be more pessimistic.