Why couldn't we heal him?

Mark
Jesus's comment about the healing of the demon-possessed boy was interesting.  See Mark 9:29 - "This kind can come out only by prayer."  He said this in response to the disciples' question about why they couldn't heal the boy.
Using God's power effectively requires a relationship with God.  Jesus had just spent a long time on the mountain, where he was transfigured and spoke with Moses and Elijah.  The majority of the disciples had remained behind, and didn't have the benefit of close contact with Jesus during this time.  Jesus, however, had just been renewed in his relationship to his Father, and so was ready to go back into the world and continue his mission.
We have access to an inordinate amount of power, through Jesus Christ, from God.  Are we remaining in Christ, and so using that power, or are we going about our way, trying to work miracles on our own strength, when we really need prayer and God's intervention?