“Reduce the effort whenever possible. The use of force is the opposite of awareness; learning does not take place when we are straining. The principle should not be no pain, no gain. Rather, it should be if strain, no gain. Feldenkrais thought the use of willpower (of which he obviously had plenty) was not helpful in developing awareness.” ― Norman Doidge, The Brain’s Way of Healing: Remarkable Discoveries and Recoveries from the Frontiers of Neuroplasticity
To give better context for this quote, it’s important to make a distinction between learning and doing.
When the focus is on learning, there is no goal to achieve other than to become more aware, so there is no need to strain or force. Reducing effort to the absolute minimum supports learning to help person become aware of what they are doing as precisely as they can, which results in their movement habits naturally improving because brain rewires itself (thanks to neuro-plasticity).
When time comes to do something, better movement habits, help reduce UNNECESSARY effort. This helps prevent strain, soreness, increases movement quality and frees up person to be more present with what they are doing.