I knew a person who once said to me that he made it a rule to never compliment other women in front of his wife. This was because, when he praised his mother's cooking, his wife took that praise as a dig against her own cooking, and it made her jealous.
Although this may be a little different from jealousy among members of the same sex, isn't it difficult to feel the joys of others as our joy, or to experience their sufferings and sadness as our own? Even if we can sympathize with another person's suffering, it's nearly impossible to be genuinely excited for a coworker, for example, who is complimented and singled out for promotion over ourselves. While the word "congratulations" issues from our lips, inside the thought comes to mind: "If that person is the one who wins kudos, what about me?"
We carry around a magnifying glass, so to speak, through which we unconsciously find people's faults.
Even when we come across a person who is obviously a cut above us, in our eyes we recognize then as only being about the same as ourselves. It's no wonder then, that we look down on people who are our equals as being far beneath us.
Isn't it true that the extent to which we can take pleasure in the happiness of other is a good barometer of the degree to which we have overdone our own self-centeredness?
From Kaisozuikan 9 (Kosei Publishing Co.), pp. 18-19