In the world of physics, we often find that the simplest questions are the hardest to answer.
You can't be creative if you're not curious.
Optimists tend to interpret their troubles as transient, controllable, and specific to one situation. Pessimists, on the other hand, believe that their troubles last forever, undermine everything they do, and are uncontrollable.
"Every man has his secret sorrows which the world knows not; and often times we call a man cold when he is only sad."