Since I am an old guy perhaps my advice has some wisdom in it.
Nobody likes rejection and it really hurts. Even if a person is "popular" I am sure they get told NO also.
I used to say that I did not care. I think saying that is natural and helps us survive the incident.
I notice that when I took up jogging my feelings, attitude and success changed for the better. There is something about that feeling of working out that makes you feel confident. I think this radiates out of a person as body language and general confidence.
Of course any kind of exercise would work I think, it's just that jogging was "in" back then and I liked it anyway.
Try it. It's free.
Also just keep busy.