"But be ye doers of the word, and not hearers only, deceiving your own selves."
The EGW quote directly emphasizes the importance of putting knowledge into practice, which is the central theme of James 1:22. Both passages warn against being merely hearers and not doers.
"There are many invalids today who will ever remain so because they cannot be convinced that their experience is not reliable. The brain is the capital of the body, the seat of all the nervous forces and of mental action. The nerves proceeding from the brain control the body. By the brain nerves, mental impressions are conveyed to all the nerves of the body as by telegraph wires; and they control the vital action of every part of the system. All the organs of motion are governed by the communications they receive from the brain. 3T 69.3"
"For as he thinketh in his heart, so is he: Eat and drink, saith he to thee; but his heart is not with thee."
Both passages connect thoughts/mind with physical well-being. Proverbs speaks of the heart's influence on a person's character and actions, while EGW speaks of the brain's influence on the body's health. The connection is thematic, not direct, but meaningful.
If your mind is impressed and fixed that a bath will injure you, the mental impression is communicated to all the nerves of the body. The nerves control the circulation of the blood; therefore the blood is, through the impression of the mind, confined to the blood vessels, and the good effects of the bath are lost. All this is because the blood is prevented by the mind and will from flowing readily, and from coming to the surface to stimulate, arouse, and promote the circulation. For instance, you are impressed that if you bathe you will become chilly. The brain sends this intelligence to the nerves of the body, and the blood vessels, held in obedience to your will, cannot perform their office and cause a reaction after the bath. There is no reason in science or philosophy why an occasional bath, taken with studious care, should do you anything but real good. Especially is this the case where there is but little exercise to keep the muscles in action and to aid the circulation of the b…
"A merry heart doeth good like a medicine: but a broken spirit drieth the bones."
Both passages discuss the impact of mental state on physical health. Proverbs speaks of a merry heart as medicine, while EGW describes how negative thoughts can hinder the benefits of a bath. The connection is thematic and relevant.