Self care includes rest and relaxation.
Living busy lives in a busy and complex world, it is easy to neglect self care in general, and rest in particular. Just as an athlete can over-train, people who seek to learn and grow can over-train - can neglect the rest and relaxation needed for learning and growth, and for the health, joy and fulfillment that is the point of it all.
Am I disciplined enough to relax? To give my mind and body enough rest? To accept that there is a healthful limit to what I can do right now, or today?