if you've ever been rejected, what's the best way to 'move on' from it

rejected online by someone you liked and hoped for friendship or something more with, or rejected in real life by someone you hoped to make connection with, i've faced these situations through life quite a few times, and you do feel 'gutted' about it, especially if you liked that person and was hoping for some kind of relationship or friendship with them....but they backed off, rejected you, because they didn't feel that way about you?

what's a way to move on from that?