Shortly after I was called as a General Authority, I went to Elder Harold B. Lee for counsel. He listened very carefully to my problem and suggested that I see President David O. McKay. President McKay counseled me as to the direction I should go. I was very willing to be obedient but saw no way possible for me to do as he counseled me to do.

I returned to Elder Lee and told him that I saw no way to move in the direction I was counseled to go. He said, “The trouble with you is you want to see the end from the beginning.” I replied that I would like to see at least a step or two ahead. Then came the lesson of a lifetime: “You must learn to walk to the edge of the light, and then a few steps into the darkness; then the light will appear and show the way before you.”

(from http://magazine.byu.edu/?act=view&a=2536, This article is adapted from an address he delivered at a BYU 18-Stake Fireside, March 4, 1990.)