It usually takes a long time to make a decision. Too long sometimes so that you actually end up deciding against doing it. You might also take too long to thing so the opportunity to do the thing might have already passed once you finally reach the decision.
The more you think the more negative things you might find against the decision. And that just makes it more unlikely to end up doing the thing. But if you don't think carefully, you might end up doing something that you shouldn't do.