If the Sun and Moon should ever doubt, they’d immediately go out.

Some things only work when they are done without hedging. A light that keeps asking whether it should shine spends itself on the question instead. That is not an argument against thinking carefully, only about where the thinking belongs: before you begin, not halfway through. Give a chosen thing your whole weight, because half commitment tends to produce the exact failure it was afraid of.

Look for one place where you are doing something and doubting it at the same time. Either settle the doubt properly or set the task down for now. Divided effort is usually the most tiring kind.