This odd turn of phrase is something you are told about over and over before going and before returning from a study abroad. I have been home for over one month now, and am not sure that I can say I've truly experienced it yet.
I would argue that culture shock itself is no that different from any social or life transition that we make. Your first day of school as a small child is, at the time, an enormous transition and causes many emotional upheavals. The same thing happens when we first move away from home, when a family member or friend passes away, or when we go on our first date. Clearly some transitions are more uprooting than others, but they all have a similar element.
What makes returning after being away so long so different is that all of those people that would have normally been a part of your transitions, have not been there. Things have not only changed dramatically for you, but also for everyone who once made up your previously much smaller world. The struggles you face are attempting to talk to a friend who you once could talk for hours with, and finding you have very little to say at all. Awkwardly you try to answer their questions about your adventures abroad, but find it is like telling your friend about a painting that you've seen. You can describe all that you want, but no one will ever understand the depth and wealth of Las Meninas without actually standing in the Prado and staring straight at it. So you describe and explain, and they smile and pretend to understand. Then you ask about their adventures over the year, and they cannot find anything to tell you. Although more than 365 days have gifted them with new knowledge, new experiences, new joys, and perhaps new sorrows, they can't find anything they want to tell you. I cannot see that in the span of one year so much could have changed for me, and so little for my friends.
For me, my transitions have been new almost once every four months. From January to April of 2012, I experienced Barcelona and being on my own for the first time. I spent time with a cluster of other students. I learned what it was like to go out to bars with other college students, how much fun it can be to dance at clubs, and how quickly a friendship can be forged with total strangers when you feel isolated.
From May until August I learned a whole other social aspect that perhaps I deprived myself from up to that point. For the first time in my life I let romance be a leading point for me. I also learned to swim fearlessly in the ocean, what it means to teach, and how much I could love British baked goods.
September until December was a time of struggle in a whole new way. I forced myself to speak in another language nearly ninety percent of the time. I discovered that helping someone else feel good was the fastest way to make myself feel good, that losing a pet hurts just as much if you haven't seen them in nine months as if you were holding them as they died.
In all, a year abroad is a year to grow, to learn, to experience and explore, to mourn, and to make friends.
Now that I am back on the other side, I already am making plans to leave again.
Perhaps that is the way in which reverse culture shock is effecting me. I do not feel a dislike for my own home, but I feel a strange homesickness for Spain and Europe.