The farmer plans for a bad year every year. Ambition with a backup plan isn’t doubt, it’s experience.

Expecting trouble and expecting failure are not the same thing. Anybody whose work depends on weather builds the bad year in as a routine category rather than as pessimism, because over a long enough run the bad year is simply one of the things that happens. Ambition without that allowance is brittle, and the first setback becomes a crisis instead of an item. Planning for it is what lets you continue through it.

So answer one question about whatever you are building: what do I do if this goes badly for six months. Name the fallback, the money, the person you would ask. Then get on with the optimistic version.