The ability to focus intently long enough to create a cell assembly, a connected group of neurons in the brain strong enough to send their signal to the hippocampus, the part of the brain responsible for making a long-term memory.
This is critical in all learning and to skill development in every domain, since each step or level of achievement to mastery, creates the platform on which the next, more complex, or larger amount of learned memories must be placed, if the skill is to be usefully applied.