Before a muscle grows, it's cells need to be broken.
If you were to quit every time you felt a little discomfort in the muscles you were training, you'd never reach your full potential. It's the people who keep getting back to the gym despite the discomfort that notice the best results.
It's true in our day to day lives as well.
No matter how many times you've fallen short of the goals you hold, it doesn't serve as evidence that you can't hit what you're aiming at on your next attempt. Maybe you've just been through the break down in order for it to build up.
Don't stop yet.