Envy according to the aspect of its object is contrary to charity, whence the soul derives its spiritual life... Charity rejoices in our neighbor's good, while envy grieve -- Thomas Aquinas
Envy isn't a simple desire for what the other person holds in their hands it's a burning acid that eats away at your heart. It erodes your affections and your motivations for affection.
When you're young being told you have a lot of potential is a good thing, when your teachers note it on your report cards your parents smile, but it cannot remain as potential forever. There comes a point where you look at that word and just feel a bitter winter of disappointment welling up inside yourself. Unfulfilled potential, it's the empty canvas nibbled at by moths, it's the fields gone to weed untilled, you had the potential and you didn't use it.
You could have.. but you didn't, it was your own dithering and wandering that lead you to being lost in the woods. No crossroads to pick between here, you need to get out the strength that you know, you know, has been lying fallow in you and make your own way. Whether you hack it out of the wilds in vicious swathes, or carefully ease your way through trying to be as harmless, non-impactful to your environment as possible... or whether you choose to curl up on the ground and give up is up to you.
You look at your friends and think: They have such wonderful things, and it all came so easily to them.
But you know, deep down it didn't, they just had something you didn't - Perserverance, and maybe passion.
I don't know how to create passion out of nothing, but I am sure it doesn't come from constant comparisons, either self or by those who love you, that you always come up on the downside of. Sure you have boundless potential, but you don't have boundless time.
When you look at the people in your life and allow yourself to be consumed by envy you don't want to see them, they make you see yourself in the dimmest light. You think to yourself I am 27 (17, 37....) and what do I have to show for it? You dip your toes in the pool half convinced it's full of piranhas. You are the donkey torn between two piles of hay, and in the end, all you have is your starvation to cling to. Except it's worse than that really, because you've become a parasite who leeches off of others...
So you put yourself away, and find petty kingdoms to feel powerful and clever in but you notice, as we all notice, time is passing, life is ticking away, every day you live is one less day of potential To Live you have... So close your eyes, take a deep breath, find yourself, find your passion.
Don't let the voices saying you Need to aim higher, you need to be Ambitious you can do anything lead you off of the track of what you want.
Find what you want, cling to it, fight for it, cleave away distractions. Find your passion and build a trail to it, it's the only guiding light in this dark world.
...
Do not envy others of what they have aspired to, you have your own mounts to climb, they are where they are, and you are where you are, but if you envy them, it eats away your energies and where you are becomes where you stay while they push forward.
And then you find suddenly you've alienated yourself from your friends, and how does one go back? It's built up in yourself into this impossible block. Mostly your friends just love you and want you back, but you, in your warped perceptions only see the bad in you (and there is bad, but don't forget it's in everyone, in that we are created -- different but equal) -- and you find yourself alone, which of course is when you start believing you ought to be alone. That you're a miasma on the life of others, but it's all self inflicted, it's the mortification of your heart, and it's unfair on those who care about you.
And you know that but it doesn't kill the trepidation you feel. The knowledge you've let people down and the fear you'll do it again. And of course the fear that they'll let you down when you open up yourself again. But if you don't take that risk life is just a hollowed shell that you stumble through in day to day routine, one day the same as the next (more or less)--
The worst sin - perhaps the only sin - passion can commit, is to be joyless. -- Lord Peter Wimsey (Dorothy L. Sayers)
Not just passion, but people, Peter, live a joyless life and damn yourself.