Getting some action seems to help a character unlock their true potential.
Do We Have This One? Sometimes a character just has to get laid. In nearly every form of culture, getting laid is considered a rite of passage. A boy becomes a man. A girl becomes a woman. Small persons of non-traditional gender become large persons of non-traditional gender. As fiction would have you believe as well, having sex can also help you achieve any task, up to and including one that may very well be physically and logically impossible. In short, this trope is when a character fails to do a task, but has sex and somehow gains the ability to achieve it or even over-achieve it. The person need not be a virgin, but if they are, it probably overlaps with Nature Abhors a Virgin (since being one was directly causing their problems). In games, this is usually invoked by Level Up At Intimacy Five. Polar opposite of Nature Adores a Virgin, Celibate Hero, and Virgin Power.
(I can't think of any examples currently, but I know I've seen this everywhere.)