It's about being a little bit of everything that makes life interesting

 

"The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails."

- William A. Ward

But can't everyone be a little of all three? Why the need to categorize?

No one is ever just an extreme, just like how no one is completely pessimistic, optimistic or realistic. In every realist, there is a dreamer. In every pessimist there is still optimism. It's not about being black or white. Sometimes grey does exist. I think people tend to forget that. 

It's all about process. First there's the complaining, but sure after we'd expect the better to come. And then we'd 'adjust the sails'. To categorize as such makes me feel like the world forces us to conform to such ideas and theories; which are just a few words on a page.

Don't let words control you. Quotes by famous personas doesn't naturally make them right.