“Jesus answered and said to him, ‘What I do you do not realize now, but you will understand hereafter.'” (John 13:7)
Of how many things that happen to us are these words true: “What I do you do not realize now, but you will understand hereafter”?
Peter — not one to sit meekly by when he didn’t understand something! — asked Jesus why He would be washing his feet. Jesus told Peter that although he wouldn’t then understand it, that what He was doing was good. He wanted him to trust Him. Some day he would see the symbolism, the significance of what had happened to him. In the mean time, he was just to trust. (Peter did not receive that well, by the way, as we see here in the next verse!)
It will often be the same way with us today: there will be things the Lord does, or which He allows into our lives, which we do not understand the purpose of, or comprehend why He would allow it. But like Peter here, our role is to TRUST the Lord, that one day we will understand it, if we do not right now. In our own puzzling situations, may we hear the Lord — Whom we have every reason to trust — say to us: “What I do you do not realize now, but you will understand hereafter.”
shawnethomas 
So many times this has been true…so much to the point that I have told the Lord, “I promise I will never question you ever again.” We are so limited in our understanding. C.S.Lewis wrote The Problem with Pain. And in difficult situations I pray that I will always see myself longing for the day when I will say, “Lord, thank you that you allowed this to happen. You are amazing. You are sovereign. You are Lord of all.” I pray my words and my life will be a testimony to this. Someone asked this question about faith, “If not now, when? If not this, what?” Sometimes difficult but so true.