The point is this: I saw more clearly than ever, that the first great and primary business to which I ought to attend every day was, to have my soul happy in the Lord. The first thing to be concerned about was not, how much I might serve the Lord, how I might glorify the Lord; but how I might get my soul into a happy state, and how my inner man might be nourished. For I might seek to set the truth before the unconverted, I might seek to benefit believers, I might seek to relieve the distressed, I might in other ways seek to behave myself as it become a child of God in this world; and yet, not being happy in the Lord, and not being nourished and strengthened in my inner man day by day, all this might not be attended to in a right spirit.
Autobiography of George Müller, comp. Fred Bergen (London: J. Nisbet, 1906), 152-4, quoted in Desiring God, John Piper, (Leicester: IVP, 2003), p. 357