I'm usually happy for other people's successes. I'm rarely plagued by envy, but I've discovered when it happens, the best thing to do is to tell the person you envy them. They'll nearly always respond with some information that kills your envy. Once, I told a flirtatious female co-worker I envied her. Coming from South America, this was the way she was raised. It turns out she was divorced (for good reason) with a young daughter to take care of - on a salary not much greater than mine. Furthermore, her ex-husband quit his high-paying engineering job and took one at a fast food restaurant to avoid alimony and child support.
I wound up being on the receiving end, which means there's something to karma. I was at snowboard camp, and wound up dancing with the pros. Later on, my counselor and a roommate told me they were jealous of me. I responded with, "Then you should have joined in! We girls are outnumbered 3 to 1 here; you should be taking advantage of it!" When I met my counselor there the following year, her attitude towards sexism in the snowboard industry had completely changed.
There is no need to tear down someone because you're jealous. Usually, if someone is successful, that's a sign that you can do it too.