You’ll never be totally certain. At some point, brave means deciding with the information you have.

Certainty is not a thing that arrives before decisions, only after them, and often not even then. Waiting for it converts a choice into a delay, which is itself a choice made by default and usually the worse one. At some point the available information is all the information there will be.

Set a deadline for the decision you have been circling and decide on that day with what you have. Write down what would make you change course later. Then act, and let the remaining doubt come along.