Sharpening The Saw
This skill is a generally unrecognized and unidentified one.
To "sharpen the saw" is the repetition of an already mostly-mastered skill. It is a form of practice. Often this action is seen in those who are bored but don't want to remove themselves from the exposure to their task.
An author with writer's block who picks up a newspaper in frustration could be seen as "sharpening the saw".
This skill is frequently seen in the actions of the hacker-type. The hacker-type, while they may be seen as obviously (even idly) skilled in a field, they are sometimes distracted to the point of frustration and find themselves slaving at tasks indirectly related to their beloved field.