I've learned that wrong needs to be pointed out but not harped on. The girls need to know what they need to correct, but when they know they have made a mistake I don't have to say anything. In fact, in those times when their heads are down I need to focus on what they are doing right, and can do. If I don't, they will surely be defeated. Jesus does the same with you.
Most people are painfully aware of their failures.
Jesus asks the Father for four things regarding his disciples. It's not the Devil and his powers because He gets to that in verse15. Whatever it is that He wants them protected from will be a threat to their oneness and unity. The greatest threat to unity is sinful human nature. Jesus has seen it in the disciples before.