How much until you become disheartened? (Details inside).

I was watching a cartoon with my baby sister. That French romantic skunk who’s always going after cats. He said “Most guys would have been disheartened by now, but not moi.” something like that.
It got me thinking. How long and hard would you try to go after someone you like very much? Not the shallow attraction in the cartoon, but when you really like someone and want to be with them.
How long before you give up, and how hard would you try?
This question is for everyone, not just guys.