One of the things currently driving me is the fact that I was accepted as a tutor on a fiction writing course not because of the 3 short stories I've sold to pro magazines but despite such a feeble publishing record. I want to sell a novel because you can't dismiss a novel so easily.
Some people seem to find strong motivation in a, "I'll show the bastards!" attitude. Others of course would wither like a delicate seedling in a drought if faced with harsh criticism, even if justified.
So it's rather difficult for a writing tutor to know what to do. I tend to err on the supportive side when giving feedback and would never say that a person should give up all hope of ever being a writer. But perhaps for some people I should? (Only joking! *g*)