Identify the root cause/underlying belief behind the emotion. Contrary to popular belief, the root cause of jealousy is not the object of the jealousy (in other words, the other person or what they have). Jealousy stems from a negative core belief about oneself. Some common negative (and incorrect) core beliefs are things like:
I am not worthy of getting what I want.
The Universe/God is not supporting me. I have to work harder than other people to get what I want, and fortune is rarely on my side.
The other person got what they have through some dubious means, or just got lucky, and is actually not worthy either. When you feel jealous, check yourself and see if at the core you believe things similar to this. Bring each belief to the surface and root out each belief, one by one.
How do you do that?