A merry heart doeth good like a medicine: but a broken spirit drieth the bones.
C.S. Lewis, Mere Christianity, p. 8:
It is only our bad temper that we put down to being tired or worried or hungry; we put our good temper down to ourselves.
Richard Greenham, A Most Sweete Comfort for an Afflicted Conscience, in Paramuthion. Two Treatises for the Comforting of an Afflicted Conscience, p. 44:
I would have wisdom both in considering the state of the body if need so require; and in looking chiefly to the soul, which so few think of.
Timothy Rogers, Trouble of Mind and the Disease of Melancholy, p. xxvi:
As Richard Greenham, in his A Sweet Comfort for an Afflicted Conscience, says, "There is a great deal of wisdom required to consider both the state of the body and the state of the soul." He says that if a man who is troubled in conscience comes to a minister, he will likely look to the soul and not at all to the body; if that same man goes to a physician, he will likely consider the body and neglect the soul. For my part, I would never despise the physician's counsel nor neglect the minister's labor, because, the soul and body dwelling together, it is convenient that as the soul should be cured by the Word, prayer, fasting, or comforting, so the body must be brought into some temperature by medicine and diet, harmless diversions, and such like ways (providing always that it is so done in the fear of God as not to think by these ordinary means quite to smother or evade our troubles, but to use them as preparatives whereby our souls may be made more capable of the spiritual methods that are to follow afterwards).
Richard Gilpin, Daemonologia Sacra: or, A Treatise of Satan's Temptations, p. 218:
Satan can afflict the body by the mind. For these two are so closely bound together that their good and bad estate is shared betwixt them. If the heart be merry the countenance is cheerful, the strength is renewed, the bones do flourish like an herb. If the heart be troubled the health is impaired, the strength is dried up, the marrow of the bones wasted, &c. Grief in the heart is like a moth in the garment, it insensibly consumeth the body and disordereth it. This advantage of weakening the body falls into Satan's hands by necessary consequence, as the prophet's ripe figs, that fell into the mouth of the eater. And surely he is well pleased with it, as he is an enemy both to body and soul. But it is a greater satisfaction to him in that as he can make the sorrows of the mind produce the weakness and sickness of the body, so can he make the distemper of the body, by a reciprocal requittal, to augment the trouble of the mind. How little can a sickly body do! It disables a man for all services; he cannot oft pray, nor read, nor hear; sickness takes away the sweetness and comfort of religious exercises. This gives occasion for them to think the worse of themselves. They think the soul is weary of the ways of God, when the body cannot hold out. All failures which weariness and faintness produce are ascribed presently to the bad disposition of the mind, and this is like oil cast upon the flame. Thus the devil makes a double gain out of spiritual trouble.