Could you elaborate on what you mean when you say you feel disconnected from others when you get back? Do you mean in the sense that you feel their understanding of the world is limited compared to yours because you've seen/experienced more of it? Or in the sense that you had a different kind of fun/adventure that they'll never experience or know about?
You go to a new place and start doing things differently. You discover better ways to do things and realize people back home don't understand what they're doing.
For example, in New York City, it seems the main activity for young people is to go out to bars and restaurants.
You pack your bags and head somewhere tropical. You pick up a water sport like surfing or kiteboarding. You start waking up at 6am with the sunrise and realize it's amazing. Back in NYC, your awake hours were more like 10am to 2am. You start cooking at home.
Now, you look back at your friends and view them as wasting their life in bars and restaurants. You start identifying with the older crowd who comes to the office at 6am or 8am instead of 11am. You also start wondering why your friends don't ever do anything outdoors.
When you move, you end up with new habits. Your brain has a need to feel correct, so it views any changes as improvements; therefore, the ways of before (and of your friends) are now considered wrong, otherwise your mind experiences dissonance. You'll find a way to justify things to stop the dissonance.
I can only speak of my own experience. My longer journeys has always been for doing voluntary work. Often that meant I got to experience these moments of fantastic joy and then the next day moments of extreme misery (not to my person but local people around me). So part of it is an emotional roller coaster. The other part is intellectual, I got to learn how other cultures and languages work, far removed from my own. I learned new ways of dealing with things in life. It sounds small now that I write it but it's truly mind expanding.
When I got back I felt that I had thoroughly changed, yet my friends and family considered me to be the same person I was when I left. How could they do anything else? They couldn't possibly know what I had been through. To them I had just been away for a (short) while. To me they started to feel narrow-minded and set in their ways. The things I now found interesting weren't interesting to them, they couldn't understand them. The things they found interesting had lost its appeal to me.
If you imagine everyone's personality is formed by their experience and strangers are strangers because you've had completely different experiences in your life - then by having different experiences than your family they would begin to feel more like strangers than before. It's not necessarily 'more' or 'less', I've been to half a dozen countries in SE-Asia and my cousins have been to half a dozen countries in Europe and America and I feel very disconnected from them.
I went on a trip to Pakistan and on return, it's like I can strike a conversation with a Pakistani/Indian/Nepali anytime anywhere but with a Chinese or Caucasian (I'm Asian Australian)? It's harder to build rapport and feel connected in conversation. It's still possible, but I notice it takes a little more time. I think it'll even out over time, though, since I wasn't in Pakistan too long.
The author of the parent comment may have a different perspective.
