If you're the kind of person who has no guts, you just give up every time life pushes you. If you're that kind of person, you'll live all your life playing it safe, doing the right things, saving yourself for something that never happens. Then, you die a boring old man.
I agree that one must persevere, BUT it's also important to know when something is no longer benefiting you. Shame in "quitting" typically comes from people trying to control your behavior.
Failure is a key ingredient for success and progress. And what a horrible fate indeed to the reach the end of your life without really ever going anywhere.