"You shouldn't whine about getting a 99 on the final instead of a 100 in
front of students who got 50's and 60's."
"Let them study harder, and besides, who tells them to be jealous."
"And Rochel saw that she was not having any children... And Rochel
envied her sister (who had a few children)." (Biraishis 30:1) Of
course, jealousy is not good ( right now, I will just say, see the
Messillas Yeshorim / The Path of the Just or the Orchos Tzaddikim /The Way
of the Righteous for ideas of how to not feel jealousy), but it IS
a "normal" human trait. Therefore, we should always be sensitive to
others' feelings and not cause them to feel jealous. (I'm not saying to
earn less money or have lower grades or not to try having wonderful
children, but not everything must be flaunted.)