Optimism is a powerful force; ultimately far more motivating and constructive than pessimism.
Optimism is not unrealistic. Especially when grounded in willingness and faith.
Optimism can change everything about footwork, making it energizing rather than tiring -- because you're moving towards something, not away from something.
Optimism fosters an open mind and the ability to see new connections and possibilities.
Optimism only irritates (or threatens?) those who feel safer being stuck in fear.
Optimism is "All I can do is try" vs. pessimism's "No point... it'll never work."
The negative voice is not "more realistic" than the positive voice. That is a sophisticated con run by those master Mental Con Men: Ego and alcoholism. Envisioning a positive outcome is an act of trust in a Higher Power and an act of faith in our own abilities. Things may not always work out the way we want, but they always, eventually, work out for the best.