I think this is one of the biggest lessons to learn in your 20s, and probably even into your 30s. Heck, maybe for life. Once you reach adult-hood, everyone's path changes. Life goes by at different speeds, and there are new opportunities popping up everywhere for everyone. You may feel that your life is changing differently than everyone else's around you, and you start to feel alone.
But it's not a bad thing. Not at all. In fact, it's perfectly normal.
So smile for the opportunities you get, and be happy that you're living a life that is your own. You are your own person now - you make your own choices, you make your own life.