Consider the core of the mind to be a wagon, with willpower to be carried about in it. Push it to a place where there can be failure, and there will be failure. Push it to a place where there can be success, and there will be success. But whether there is success or failure, if one entrusts himself to the straightness of this wagon of the core of the mind, he will attain right-mindedness in either case. Severing oneself from desire and being like a rock or tree, nothing will ever be achieved. Not departing from desire, but realizing a desireless right-mindedness, this is the Way.
From The Unfettered Mind: Writings from a Zen Master to a Master Swordsman by Takuan Soho, translated by William Scott Wilson, page 54