Rejection sucks for everyone! Mainly because we have expectations that are false or assumed. To put it simply, you aren't going to be everyone's cup of tea (no judgement for what reasons they have, all their reasons are legit). So the best thing to do is accept that. Say to yourself, "hey, I am my own person, and not everyone is going to like me for who I am. I know that, but there will be someone who I like, and they might like me back too in the same way!"
And alongside of the 'never give up' encouragements, remind yourself that if someone regects you, then that means you're one step closer to finding the right person for you.