We know very little about self development. But we do know one thing:

people in general, and knowledge workers in particular, grow according to the demands they make on themselves. They grow according to what they consider achievement and attainment.

If they demand little of themselves, they will remain stunted.

If they demand a good deal of themselves, they will grow to gain stature - without any more effort than is expended by the non achievers.

Peter F Drucker