Good as such cannot make a person sad, but one can be sad about good as understood under the aspect of evil, whether real or apparent. And envy in this way consists of chagrin at the good of another, namely, insofar as the good of another is an impediment to one's own excellence.
Thomas Aquinas, De Malo 10.1 ad 6.
[Thomas Aquinas, On Evil, Regan, tr., Oxford University Press (Oxford: 2003) p. 353.]
