A tranquil heart gives life to the flesh, but envy makes the bones rot (Proverbs 14:30, ESV). The word envy is to be understood in contrast to the idea of tranquil. When I think of tranquil, however, I think of something more like stress free. Everyone to some varying degree feels stress; the teacher does, the parents do, the preacher, everyone. Stress is that occasion where tension rises, the muscles tighten, and the stomach feels a little unsettled. For some, this turns into a headache that possibly immobilizes.
Maybe, when we think about stress in this context we are actually thinking about envy. Envy is defined as a painful or resentful awareness of an advantage enjoyed by another. Envy, left unattended, is a canker sore that does not die until the death of the one plagued results.
Stress and envy are not necessarily connected, but perhaps there is more connection between them than one normally thinks. When I feel stress I can say that envy is not part of my thinking – at least not that I am aware. What would I envy? A tranquil heart.