It is very important advice that if the jealous mind arises when you see someone smiling or talking to another person, then you can think, “Everyone is most precious and most important—just as I think I am, they also think in that way. Just as I want happiness and think I am most important, like that, everyone needs happiness and needs the best happiness. How wonderful it is that this person has achieved happiness.”
You can rejoice so much and in that way transform it into happiness. That is very positive; that is holy Dharma.