“[There is] a beautiful insight, quoted in the name of the Chidushai HaRim.
The Gemara in Meseches Ayrachin tells us that there are a number of avayros [sins] which can cause tza’aras. The most commonly known avayrah is loshon horah [evil tongue; slander].
However, the Talmud in Meseches Ayrachin also says that the punishment of tza’aras comes ‘al tzoras ho’ayin.’ Tzoras ho’ayin [literally – narrowness of eye] does not only mean a person who is tight-fisted or cheap. A tzar ayin is a person who never sees the good side of anything and always sees evil. It is the opposite of a generosity of spirit. It is a stinginess, not only regarding money, but regarding viewing life, in general. A tzar ayin is a person who does not like to see other people’s success. The only success that he is interested in is his own success.”