The negative person vs the chronic complainer

An optimist sees a glass half full of water. A negative person sees the glass as half empty. The chronic complainer sees water that isn't cold enough, sees the smudge on the rim, which means the glass wasn't cleaned properly and wonder if they will end up with some kind of virus.

Chronic complainers may not have a negative outlook on life but they want everyone to know that nothing is ever good enough. In their mind, the world is what's negative, and they are only aware of one way to respond to it. They don't know how to express themselves in a positive light.