wellspring

noun

1. The source of water for a stream, spring or well; a fountainhead; a wellhead.
2. (figuratively)A perennial source of anything; a fountainhead of supply or emanation; resource.

   “We’re so often taught to simply believe in ourselves—to trust our instincts—that to see a narrative in which second-guessing oneself and refusing one’s deepest impulses is a potential wellspring of charity and good is, in itself, noteworthy.”

   “Krapp’s Last Tape has been acted by prisoners in San Quentin and made into a chamber opera. It goes to the wellspring of an actor. Well, most of the time: when Albert Finney played the part, Beckett went to sleep in rehearsals.”