Life’s allure lies in the uncertainty. anxiety is the pessimistic response to the unknown.
Optimism, the feeling, does not need to depend on P(success). You’ve already committed. What do the odds have to do with your ability to follow through? P(setbacks) = 1, so expect them and prepare.
You can have conviction without self-deception, i.e. you can know your odds to be 1/3, but still fill yourself with confidence in order to focus and perform at your best. You can still tap into that mental state.
Optimism won’t always carry you to victory, but pessimism guarantees defeat. See expectancy theory.