I am enjoying the book "Life with Picasso" by Francoise Gilot and Carlton Lake. Gilot was (still is) an artist herself, 40 years younger than Picasso, and a very strong woman.
One of the things he told her:
"You must always work not just within but below your means. If you can handle three elements, handle only two. If you can handle ten, then handle only five. In that way the ones you do handle, you handle with more ease, more mastery, and you create a feeling of strength in reserve." (p. 50)
Just the opposite of 'aim for the moon, you may land among the stars' or 'work at the edge of your capabilities; that way you learn something new'. And it has a truth in it that appeals.