Agree completely with rationalising.
I think the hardest part of jealousy is when other people start comparing you (even right in front of you), you ever had that before? I've heard people gossip about me at a restaurant comparing me to the successes of other people my age who we knew. That is the worst part of it, I can deal with the actual occurences of jealousy myself, but cannot stand it when other people actualy verbalise comparisons between me and others. I never do that myself, meaning i never gossip and compare people because i have empathy, so i sort of start to lose respect points when i hear people gossiping.
Anyway, one thing to remember is that, if you are jealous of something then perhaps look at it as "it wasn't meant to be" and move on swiftly. Hard to do i know, but just say you have a crush and someone else comes onto the scene who are too good to be true, it is a sign to just full stop that entire world, perhaps offer to still be friends but lose that sense of having a crush and move on. Remember there are many other fish in ......well you know the rest.
jealousy of success of a skill is another issue. The only reason someone gets skilled at something is because they practice daily, they make loads of mistakes but they will improve like anybody. They are not geniuses, they just practice alot and they may have alot of other issues themselves that they hide well.