"Once the arrow left the bow, there is nothing you can do to change its path. So, why worry about it? Focus your attention on the next one. Feel the tension on your back, and slowly relax your finger. Take notice of your stance, and become one with the bow. You should feel how heavy it is, and how close the string is to escaping your finger. Let them, and don't fight back. Feel how smooth that release was, savor it, and focus your mind on the next arrow."
or if I am to paraphrase it, "So what? Next arrow."
--My archery coach--
That quote actually helped me through high school and university, because I was quite depressed after a really bad exam. But, well, can't do shit to change it now, but I can change the next exam if I don't linger on the old one, and focus on studying for the next one.