John MacArthur noted “Perhaps the best way to illustrate the idea of ceaseless prayer is to compare it to breathing. Inhaling and exhaling is so natural for us that it often seems totally involuntary; it’s actually harder to hold your breath than to breathe. The same should be true of prayer for the Christian. Prayer is like breathing for us. The natural thing for us to do is commune with God. When we don’t pray, we’re holding our breath spiritually-fighting against the very existence and presence of God in our lives. Prayer should flow naturally and continually from our hearts.
When Paul commands us to pray without ceasing he doesn’t expect us to walk around with closed eyes all the time, nor does he mean every prayer should last an hour or more. What he does mean, however, is that we should be in constant communion with God”.
(John MacArthur: Lord, Teach Me to Pray: Countryman. 2003. p. 49).