Our sinful nature places the blame on others, but we must take the responsibility for our own personal reactions to problems. It is a quick process. Put a drop of black ink in a glass of water and it will discolor the whole glass of water. In the same way, bitterness works quickly to hurt everyone involved in trying to help the patient. Our resentments call forth certain hormones from the pituitary, adrenal, thyroid and other gland.
Excessive hormones can cause disease in any part of the body to complicate the healing process.
Major hindrances to spiritual development take place. It requires emotional energy to maintain resentment. The moment I start resenting a person, serious mental consequences occur. When I'm served steak and potatoes it might as well be bread and water. Bitterness can be healed by forgiveness.