Eight-ninths of the bulk of an iceberg is below the waterline and out of sight. Only one-ninth is visible above the surface. Our prayer life should be like an iceberg, with about one-ninth showing in public group prayer and eight-ninths out of sight in our personal prayer time.
Michael P. Green, ed., Illustrations for Biblical Preaching: Over 1500 Sermon Illustrations Arranged by Topic and Indexed Exhaustively, Revised edition of: The expositor’s illustration file. (Grand Rapids: Baker Book House, 1989).