From a letter to Mr. B—-, 6 November 1777:
MY DEAR SIR–You say you are more disposed to cry miserere than hallelujah. Why not both together? When the treble is praise, and heart humiliation for the bass, the melody is pleasant and the harmony good. However, if not both together, we must have them alternately; not all singing, not all sighing, but an interchange and balance, that we may be neither lifted too high nor down cast too low, which would be the case we were very comfortable or very sorrowful for a long continuance. But though we change, the Saviour changes not. All our concerns are in His hands, and therefore safe.
(John Newton, 1725-1807. English pastor, author, and hymnwriter, noted especially for writing the text to “Amazing Grace.” As well as being good spiritual insight, this is fine advice for composers, of course.)