Keller challenges us to consider why we don't go to Christ in prayer--why we avoid being strengthened through the power of Christ's Spirit in  communion with him in prayer. Why don't we allow his Spirit to work through us as thoroughly and completely as he can?

My response is to get down on my knees before the Father, this magnificent Father who parcels out all heaven and earth. I ask him to strengthen you by his Spirit - not a brute strength but a glorious inner strength -that Christ will live in you as you open the door and invite him in.

And I ask him that with both feet planted firmly on love, you'll be able to take in with all Christians the extravagant dimensions of Christ's love. Reach out and experience the breadth! Test its length! Plumb the depths! Rise to the heights! Live full lives, full in the fullness of God.God can do anything, you know - far more than you could ever imagine or guess or request in your wildest dreams! He does it not by pushing us around but by working within us, his Spirit deeply and gently within us.Glory to God in the church! Glory to God in the Messiah, in Jesus! Glory down all the generations! Glory through all millennia! Oh, yes! Ephesians 3

"When Paul prays for the Ephesian church, he does not pray for an improvement in their external circumstances. Rather, Paul prays for God to grant the members of the Ephesians church a profound internal knowledge of the depths of God's love. Paul prays that the doctrines that the Christians intellectually believe would become experientially real to their hearts."

http://sermons2.redeemer.com/sites/sermons2.redeemer.com/files/sermons/When_I_Survey.mp3