As regards what we experience as pain and sorrow, it is seen on the spiritual plane that the pain and sorrow we have borne on the physical plane work on and permeate our soul with such force on the spiritual plane that this force becomes will-power. Our soul thereby becomes stronger, and we are able to transform this strength into moral power which we are able to bring back with us again to the physical plane, in order that we may not only have certain capacities, through which we are able to produce something of value to the world around us, but that we may also have the moral power to develop these capacities into character.
Source: Rudolf Steiner – GA 153 – The Inner Nature of Man and Life Between Death and Rebirth: Lecture 6 – Vienna, 14th April 1914
Translated by Harry Collison
The great Rudolf Steiner Quotes Site 