People of mediocre ability sometimes achieve outstanding success because they don't know when to quit. Most men succeed because they are determined to.
“I'm so glad I'm not a dentist. How many times does someone say, 'Oh, Doc, it felt so good when you were drilling my teeth'? Never. But when you give someone a wonderful cookie, you put a little of yourself in, and you see someone's face light up - that's immediate approval.”