Take yesterday afternoon, for example. There was a half-finished short story sitting around here, and there was a fistful of dark-chocolate-covered almonds left in the pantry. If I'd conceived of the almonds as a reward, I guarantee I would not have finished the story, and I would have had to depart for dinner grumpy, with the beginnings of a hypoglycemic headache. And I wouldn't have gotten to eat the almonds. Pessimal outcome. As things stand, I used the almonds for fuel and sat down at my desk basking in dark chocolate and almonds. And when I looked at the clock again, the story was done and there were ten minutes left until I was supposed to leave for dinner. And no headache. And I had enjoyed the almonds.
In this case the fuel is rather literal, but it doesn't always have to be that way. Sometimes a leaf-scuffling walk with the dog is fuel, or time making music, or a trip to the library, or a minute to sit and be quiet with your head on someone's shoulder. I don't do well with hostages towards my own good behavior. I do far better with trust expressed in my own better nature. "I know you're going to work hard on this story, so here are some chocolate-covered almonds to help you along," sort of thing. "Here's a nice cup of tea to make the revisions go smoothly." "Stretch your legs and shoulders out in the nice cool air -- you'll want them loose if you're going to really sit down and hammer out some rough draft here." Like that.
If you're taking a 4-year-old on an airplane, she might behave herself if you promise her a new puzzle and a new coloring book afterwards if she does, but your odds are better if you give her the puzzle and the coloring book to help her be good on the plane in the first place. The part of the brain that makes stories come out is not a preschooler, but some days the reactions are not as dissimilar as one might hope.