Parshas Yisro: Do You Really Want What Your Friend Has?
The Meforshim explain, it is coming to teach us how to prevent jealousy towards a friend. One might look at a neighbor’s wife and see how wonderful she is. One might look at his house and see how well he lives. One can look at his job and his children and think “This guy really has it made!”
The Torah is telling us to consider “kol asher l’rei-echa” — look at the whole picture. Everyone has his or her own “Pekeleh” of problems in life. No one’s life is perfect. As apparent as it may seem that this person has it ‘made’, we do not know the whole story. We can never know for certain. It is always necessary to take into account “kol asher l’rei-echa” [all that is doing with your neighbor].
from Revach.net