A question often arises about usefulness. Satan often beguiles by it. He may have suggested to John that he would be more useful if he were to compromise a little, and keep out of trouble for the sake of being free for his service to the saints. Useful to whom? To God or to men? God may be able to show out more of His glory by laying men aside. The eyes of God rested on Paul a prisoner, seemingly useless (not even always allowed to write), as the field for the display of some of the greatest privileges of truth. The very point when your weakness seems to make you useless is often the very way in which God shows forth His glory.
People think it strange that old Christians, useless ones, etc., etc., should be left, and young active ones taken. Do not you be trying to settle God's house for Him; do. not say, "What a pity for John to get to Patmos." The Lord wanted him there to communicate something that might serve His people to the end of time.
A person may be in difficult circumstances, and you may have it in your power to get him out of them in the power of human nature. And you may do it, and find out that God would have had him in them, because then he could have borne testimony; and you ought not to have measured things by your love for him and your comfort, but by the light of God. We often act on a set of thoughts of which the cord is bound to our own humanity instead of God's glory.