Two words that are not the same word
There is a term people reach for here and it is usually the wrong one.
Hasad, in the technical sense, is wanting a blessing taken away from the person who has it. That is a serious thing and it is not common. What most people actually feel looking at a friend's holiday photographs is closer to ghibta, which is wishing you had something like it without wanting them to lose theirs. Or it is plain deflation, which is not even a wish.
Calling ordinary deflation hasad puts a sin on top of a feeling. That is the second layer. The second layer is what this whole course is about.