A very important piece of advice is keep your eyes on your own page. Don’t compare your career to that of others. There are a variety of variables in a writing career.
I would like to second, third, and fourth that. And I agree with Steve’s comment that it’s easy to say and hard to do.
But even though wallowing in envy isn’t useful and doesn’t make one pleasant to be around, that initial twinge of envy can be motivating. Someone sells a story to a market I’d love to crack? Maybe they put three times as much time into their writing than I do, and therefore get a lot more practice. Maybe they’ve worked harder to learn techniques that I’m struggling with. The solutions to both those problems are pretty obvious. (Maybe they’re just more talented than I am, but there’s no point in thinking about that.)
So, while envy is hard to avoid, it does have its upside. Acknowledge it, use it, and move on.