"It's that if you want to make a human being into a monster, deny them, at the cultural level, any reflection of themselves."
~Junot Diaz
When I left graduate school, I came home for three years with no one that I could have the kind of intellectual connection with I had at college. It was like I was speaking a foreign language to my family and coworkers. Of course, I could go on the internet and talk about my computer stuff, but it's not the same when you are with people you trust your understanding of your knowledge with.
It's scary, and I'm still clinging to my own sense of self, even though I don't get to know whether it's still there, every single day. But I won't be marginal.
Your family, friends and coworkers are what is real in your life. I know it's probably not your fault, but graduate school has this nasty effect of absorbing every bit of mental "energy" from the students. Your connection to the rest of your life gets starved and your identity becomes whatever you research.
Then, if you don't happen to be from the very lucky who get tenure, you get thrown to the wolves into a world that cannot and will not understand you. I could tell you of the time that I almost cry in my first (grossly overqualified) job because I could not figure out how to use the damned phone.
I am not telling you to leave behind whatever is you found in graduate school. You can always make a special place for it in your life. But the way forward is to make your life broader, by nurturing aspects and relationships that have been neglected so far (or creating new connections if some of the older ones got broken beyond repair).
At the end, you will become a happier and more interesting human being! :)