Proverbs 18:14 The spirit of a man will sustain his infirmity; but a wounded spirit who can bear?
The spirit inside a person is in some important sense, stronger than the body. The promise is that the inner man (where God’s Spirit dwells) will keep you going when the outer man is weak. When sickness, injury, and pain are attacking the body and rendering it infirm, sustaining strength will come from a live and healthy spirit to keep you going.
The condition in this verse is a “healthy spirit,” for if the spirit itself is wounded and weakened it cannot help the body, and the body does not sustain the spirit. Therefore, no one can bear it when both body and spirit are weak and wounded. The obvious answer is: feed, nourish, and care for the spirit to keep it strong and healthy. Then the Spirit in the spirit will be strong to sustain.
We already know how to keep the spirit spiritually strong: feed it with the Gospel as often as you can, and you can’t overfeed it. Go to church, attend Bible study, and be faithful in private prayer and Bible work. The forgiveness of sins heals over the wounds caused by sin, makes us strong, and sustains us when infirmity comes. Wounds can be self-inflicted or inflicted by others. Either way, forgiveness received and forgiveness given makes the spirit strong to sustain our infirmities.
The Spirit of God is working to heal messed up emotions and beaten up bodies. It always helps to trust the spiritual God alongside the physical science to sustain our infirmities. That’ the promise.