Too many learn a skill to simply cram for a test or presentation instead of trying to actually understand it fluently
Skills attenuate with disuse.
Throughout his life, a wise man engages in practice for all his useful, rarely used skills, may of them outside his discipline, as a sort of duty to his better self.
Skills of a very high order can be maintained only with daily practice.
Use-it-or-lose-it tendency postulates that When a skill is raised to fluency then the skill (1) will be lost more slowly and (2) will come back faster when refreshed with new learning.