When I said I aspired to be the Grandma Moses of literature yesterday, I wasn't just whistling dixie! According to the American Heritage Dictionary, to "whistle dixie" is "(to engage)] in unrealistically rosy fantasizing". Usually, it's used in a negative way..."Don't just whistle Dixie", for example, means "Don't sit around wasting time". It comes from the popular southern song, Dixieland. Whistling Dixie is akin to self-delusion and daydreaming.
Jesus said, "No one who puts his hand to the plow and looks back is fit for service in the kingdom of God" (Luke 9:62). To put your hand to the plow means to begin the task of plowing.
Jesus probably isn't saying you can't glance back. But he IS saying you can't continue to look back once you've begun to plow. If you do, you're not "fit"-- suitable, usable, convenient for something.
Words my art.
The pen my brush.
Paper my canvas.
Punctuation my nemesis.