Chinese medicine holds that when your vital energy is strong, illness has no easy way in.
Tips
culture
The moral sense leads. It is the force a person is felt to carry, and it has a standing opposite, 邪气. Official and workplace language uses 弘扬正气 for promoting decent conduct and squeezing out the crooked kind.
usage
Traditional medicine borrows the same word for the body's own resistance, the thing that keeps sickness out. Context separates them cleanly: a person or an organization has the moral kind, a body has the medical kind.