So what can you prove?
At some point around preschool-age, you developed a realization of existence.
You’re surrounded by a cast of characters.
You’re experiencing a personal story that’s tucked within several larger narratives.
A bad attitude causes you to feel bad.
A positive attitude causes you to feel better.
Enjoyment is the preferred state-of-being when compared to all others.
You have memories, but memory is a faulty mechanism fraught with interpretation issues, problems of perspective, and decay.
First, you can conclude you’re within a story populated by a cast of characters. Second: striving to enjoy this narrative is the best use of your efforts. Third: in order to enjoy something, it must be performed with a positive attitude. And fourth, the past is based on shaky assumptions and can’t be used as a predictor of future events — so the only thing you can rely on is “right-now”.
What all this boils down to is this: by fine-tuning your immediate attitude, you are in direct control of your happiness in every moment. If you choose to interpret right-now in the best possible way, you will enjoy life. Therefore, the logical path through life necessitates the cultivation of happiness through the development of a positive perspective. Q.E.D.