giving up

How many times should you fail at something before you give up? Maybe never. Maybe you keep getting back up and trying again. That's at least what they tell you when you're in elementary school. How many times do they tell you something like: "you can do anything you want if you put your mind to it"? I've certainly heard it lots. But what does that really mean? What if I don't know how to put my mind to something? Then how do I get what I was looking for? And what is that phrase supposed to apply to? Is it supposed to mean that I can be a doctor, an engineer, a teacher, or a salesman? I would make a terrible salesman but then again I've never had any desire to be one. Does it only apply to jobs? Or can it apply to relationships to? Can I be a wife or a mother if I try hard enough? My pessimistic side says no. That's crazy. Just because I want to get married some day doesn't mean I can. Or perhaps I can if I don't care if I'm happy or not. I guess I could just marry the first guy who would take me, but maybe there isn't even one of those. And there's no saying I can have kids either. If there is something wrong with me so that I can't have children that makes things tough, but then maybe I could adopt. But at some point you give up right? There are only so many options and so much money. You can only fail so many classes before you decide that a profession just isn't worth it. And you can only chase after someone for so long before you finally take the hint that they're not interested. But what if you go for something and get it. And then it sucks or you're just not good enough for it. How long do you pretend that you are good enough before you give up? How long can you convince yourself that you belong somewhere that you clearly don't?