Try actively steering your fantasy past the peak of infatuation and into the latter stages of a relationship and on to breakup.
Right now, you have intrusive thoughts about falling in love with them, and probably the excitement of getting to know someone intimately. Instead of trying to hold back, let that fantasy play out in your head further. Imagine moving in, imagine them not getting you when you're explaining your problems. Imagine liking them, but finding their bad habits increasingly intolerable, and never being able to pick a movie to watch. Imagine them not flushing the toilet and clogging the shower drain with hair. And then imagine meeting someone new, and feeling guilty about crushing had on them. Imagine this new person reciprocates, and imagine politely explaining to your dance instructor that you guys can stay friends but, the romance has run it's course.
And there you are. The itch is scratched, and in your mind they're just a friend again.