"But know this first of all, that no prophecy of Scripture is a matter of one’s own interpretation, for no prophecy was ever made by an act of human will, but men moved by the Holy Spirit spoke from God." (2 Peter 1:20-21) Both planned and spontaneous worship can be utterly Spirit-less. But if your deliberate planning and your spontaneous actions are soaked in rightly interpreted Scriptural truth, they both "leave room for the Spirit." In fact, I'd say we should be asking God to leave no room for our own preferences but that we would be so full of the Spirit that all of our worship -- planned and spontaneous -- is just the overflow of a heart that knows Him. Of course, that takes humility, and humility is hard.