As a preacher, I'm regularly asked how long it takes me to write a sermon. My go-to answer is, "It depends on how much I've prayed." I see a direct correlation between the quality of my preparation/preaching and the quality of my praying.
For many pastors, myself included, prayer can be the easiest aspect of sermon prep to skip. This, however, is a grave error. The preacher preps the sermon, but prayer preps the preacher. Prayer is what prepares our hearts to proclaim God's Word. Prayer is what gives preaching power in the pulpit.