From page 10 of Tim Keller's Redeemer Church Planters Manual, on Keller's call to plant in NYC...
A great darkness descended on me, because I knew I had no good reason not to [plant in NYC], but I felt totally inadequate for the job. I know that everyone feels inadequate for any ministry, but this was different. I knew that I was as humanly well-equipped as anyone to try this ministry, but I also knew this was well beyond the human abilities of anyone at all. That meant only one thing: it would not be my talent, but my love for, and dependence on, God that would be the critical factor in the project. I felt that my spirituality would be laid bare for all (worst of all, for me) to see. But the opportunity was too ripe and I also knew it was a door that might not be open for even a few more weeks...
I prayed and was reading Gurnall's A Christian in Complete Armour one day and came upon a passage: "It requires more prowess and greatness of spirit to obey God faithfully than to command an army of men; more greatness to be a Christian than a captain." I realized that if was an illusion to imagine that I would have to start being brave if I took this job; I should have been living bravely all along. Even if I turned the NYC church down, I could not go back to being a coward. So I might as well go to New York! On July 1, [1988], I gave Westminster Seminary a year's notice. Immediately, my prayer life broke open like never before. I did not wonder why.