to apply oneself conscientiously to one's work.
it is similar to the idiom of keeping your nose to the grindstone in both meaning and logical origin (or lack thereof). Essentially, it is the 'grindstone' saying adapted to the 21st century, and more specifically applies to the elimination of procrastination tendencies, i.e. do work son.

When you eat dirt for the first time and leave your family to build a shack in the woods