Following Jesus seemed easy enough at first, but that was because they had not followed him very far. It soon became apparent that being a disciple of Christ involved far more than a joyful acceptance of the Messianic promise: it meant the surrender of one’s whole life to the Master in absolute submission to his sovereignty….This was strong teaching. Not many people could take it. They liked to be numbered among his followers when he filled their stomachs with bread and fish, but when Jesus started talking about the true spiritual quality of the Kingdom and the sacrifice necessary in achieving it (John 6:25-29), many of his disciples “went back, and walked no more with him” (John 6:66). As they put it, “This is a hard saying: who can hear it?” (John 6:60). The surprising thing is that Jesus did not go running after them to try to get them to stay on his membership roll. He was training leaders for the Kingdom, and if they were going to be fit vessels of service, they were going to have to pay the price.
Robert Coleman, The Master Plan of Evangelism (pgs. 50-51).