Hindsight gives you perfect vision after the exam is already graded. Practice looking earlier.

Afterwards the signs look obvious, because you now know which ones mattered and can ignore the hundred that did not. That clarity is not yet wisdom. It turns into wisdom only when you carry it into a situation that is still undecided, which is much harder and considerably more useful.

After something ends, write down the earliest moment you could have known. Two lines is plenty. Do that a few times and you start catching that moment while it is still happening, which is the entire point of looking back.