What do you do when you don't want to move on?

Asking both girls and guys. Say you have a crush on someone. He/She likes someone else or doesn't like you generally. Many people tell you you can't change that fact but you don't want to give up on that person because you still believe something might change and like him/her a lot. What do you do at that point?

PS: I'm not sure if this question should be in 'Social Relationships'. Correct me saying a more appropriate topic to ask such questions.
Updates:
+1 y
I don't have a problem of my own I just want to hear opinions from different ages.
+1 y
So from current opinions none of you would try some more?
What do you do when you don't want to move on?
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