Blood has been shed needlessly over this verse. Contention is so sharp wars have been waged. Was the rock Peter? Catholics say so in their argument for Papal succession. Was the rock his confession or revelation of Jesus Christ? Evangelicals say so.
I wish to sidestep the debate completely and focus on the main point. The central idea here is that Christ will build his church, not man. When you are a ministerial leader, you get the sensation that you are building your ministry. That sensation is strong until you fail. When you are fighting a war of attrition, then you want to reach out and find some sort of help. You remember that it’s God’s ministry, not yours. He will build.
Prayer focuses the True Builder of his church, although we humans wrongly feel we are building. In other words, get more involved the Guy who really does, and get yourself less involved (I was a ministerial work-aholic). Pray more.