Stop a minute, right where you are. Relax your shoulders, shake your head and spine like a dog shaking off cold water. Tell that imperious voice in your head to be still.
Let's say music is needed for only 43 seconds of film. You have to score it so it is an entity, so it won't bother anyone when it ends so quickly. Or if a song runs 2 minutes and 45 seconds, but the titles run a minute longer, you have to arrange that song so it doesn't get repetitious.