Notice how much Peter wants to be like Jesus. He wants to do the things that Jesus is doing, but Peter is still missing something.
His faith is not the same as that of Jesus. Peter does not have the same interior life as Jesus. Peter does not have the same relationship with the Father as Jesus yet he wants to be the same externally.
Maybe we, too, miss the part about going to the mountain to pray as Jesus prayed and so miss out on a deeper relationship with the Father. What can we do to make a change?