Certainty feels like strength and often works like blindness.

Being sure has a cost that does not announce itself. Once a question feels settled, you stop collecting information about it, and everything that would have corrected you arrives at a closed door. The feeling is pleasant, because certainty is comfortable and doubt is not, and that comfort is exactly why it is dangerous. Strong opinions held loosely are much harder to hold and much more useful.

Take one thing you are completely sure about and go looking for the best argument against it, not the worst one. You are allowed to end up unchanged. The point is to find out whether you are still deciding or just repeating.