Better still to think about the expected value of optimism vs. pessimism. It's good to have well calibrated likelihoods of success, but it's also good to remember just doing things which might succeed feels inherently good.
I would like to go further and state that just optimism by itself feels inherently good.
Even though pessimism can minimize impact of all kind of negative future live events, it won't make you any happier if you will always be as pessimistic as you are now.
