When I go to my home group meeting at the BARN (Bangor Area Recovery Network) there is a little sign just inside the front door "Nothing is impossible to a willing heart" - it's an affirmative message to me.
It's part of my three words, Acceptance, Willingness, and Gratitude - my most powerful tools, they could help you too if you're not already using tools like that (lot's of people have their own favorites).
If you're new to being "a quitter" you may find using these kinds of tools useful - give it a try.