I upvoted an answer too hastily. When I realized that the answer was wrong, I tried to cancel my upvote with a downvote. However, that simply replaced my upvote with a downvote (at a cost to the reputation of the answerer and myself). The answer, while wrong through its incompleteness, wasn't so bad as to warrant a downvote, in my view; it just didn't deserve an upvote in its present state. So, in particular, is there a way just to withdraw an upvote cast in error for an answer? More generally, is there a way to neutralize any of one's mistaken votes, within a reasonably short time, leaving no net effect on anyone's reputation?
If I may anticipate one type of answer to this question: the solution is not to vote in haste. This is a lesson I have already tried to learn.