To give up and try again before the completion of the first attempt.
If at first you don't succeed; Shep it.. but only once. Then you are out of sheps
When driving in Mario Kart:
*Falls off the edge*
You: " Fuck man I Shep!! start the race over!"
you: "I'm gonna Shep it man!"
Me: No you can't you are out of sheps!"