Consider your crush from a realistic point of view.
That is, stop idealizing and romanticizing your adored object. And this hook can be especially easy to fall for if you are not so familiar with the person. Because we usually show only our best sides in public.
But if you soberly assess the situation, then your beloved is the same as everyone else. Yes, with its pluses, but it certainly could not do without minuses. To help yourself overcome romanticization, write down all of its negative qualities on a piece of paper. And contact him from time to time. Especially when you again want to think that “you will never meet such a wonderful person again.”