This is so true! You can hang on way after you think you are going to peel. I find gym climbing helps me here, as I learn precisely how long i can hold onto a certain hold.
Also, being able to find a centering routine, where when I feel pumped out, or I'm in over my head, to smile, relax, and say hello to fear and accept it, get some gear in, and continue! Calling "take" can be so tempting once you get that gear in but you know you can keep going!