There is greatness in the everyday ordinary. My grandfather was a great man who had hundreds of people at his funeral, but nobody will ever write a book about him (not even an article in the local paper when he passed away). He was genuine, friendly, always ready to lend a hand, and had a no-kidding money tree in his back yard with coins growing out of it.
I think the key to your happiness is re-evaluating your definition of greatness. Do not be defined by what you do, but by who you are. Maybe volunteering would help, or joining a new meet-up group. Up through your early twenties there is always something new and different just a few months or years away. You could conceivably be doing what you do today for the next 30 years. Maybe somewhere in the back of your mind the idea of having nothing new scares you and makes you feel like you are bumbling.
Yep, I was there at 22. I started a full-time job for $40k a few weeks after graduation. My first day on the job (as a fleet supervisor for a trucking company) the word I heard the most was "retirement", mainly from my well-meaning coworkers trying to give me advice. I went home thinking that everyone at my new company must hate their job if all anyone thinks about is the day it will all end. My mind was hung up on, "Is this all there is? This is going to suck."
1. I changed jobs. Part of my problem was job dissatisfaction. I hated my job and felt like it did not make a contribution to society. I did some soul searching and figured out what I enjoyed, then shifted careers. I have way more fun doing what I do now, but there are still days when I sit and wonder if I am maing the world a better place. But, we take ourselves too seriously as adults. Who says we all have to find a cure for cancer? It should be enough for us to make one person smile each day.
2. I found new hobbies. I took up Spanish, running, and things I thought were awesome as a kid, I went back into it. Mountain biking, making bike ramps in my driveway, pillow forts, animated movies.
3. I had kids. I mean, we had planned on having kids anyway, but when they came along, it helped the feeling of bumbling. New parents achieve greatness overnight (for dads, for moms it probably feels more like nine monhs). Everything you do can make their day.
It passes, and as a few have suggested it's just a matter of perspective.