Being envious of what other people, including your friends, have will get you nowhere because the grass always LOOKS greener on the other side. In reality, it is greener wherever you water it! Everyone is on a different life path! When your friend gets married, you should be truly happy for them because this could be the love of their lives; being jealous of your friend getting married isn't great though. However, just because your friend is getting married now, doesn't mean that you won't get married in the future. So, recognize that you're envious and then try to move on and be happy for her as a good friend!
Of course, getting married is just a random life example. There are so many things that you could envy your friends over, but you should do your best to be happy for them! It's easy to be envious when other people's lives are going great, but your moment to shine will be here! Your friend's success does not automatically equal your failure. It just means you are both on different life paths with unique timelines.
Your life has its own timing and when you're destined to do something, it IS going to happen! And your friends will be there for you and smiling, just as you were for them. We all have different timelines and certain BIG life moments will happen at different stages in our lives than our friend's lives. Just recognize that if it's something you truly want, all you can do is give it your all and hope that it works out for the best.
Try to be patient and live in the present moment, because it'll all be worth it when your time comes to shine.