Because we never put full effort we can never know what we are ultimately capable of. At some level we are afraid that we might discover we are no good at something, so we never try OR we try with partial effort so that we continue to dream. It’s almost like we are divided in such a way that a part of us purposely prevents us from putting full effort since it’s very afraid of failure or hiding from us some deep unpleasant truth. That’s why full effort totally allows you to see what you is true and what is not with far greater clarity. In fact full effort = quite analogous to perfect clarity on whatever it is applied to.