I was beginning to have the same experience when I was living in Kyiv. When that feeling of nostalgia starts to hit and you think the past was always better, you begin resenting those coming and experiencing the place for the first time, then you should know that it's time to move on.... Unless of course you've put down some serious roots, marriage, kids, a business etc.

I love staying in the same place for extended periods, but there's always something exciting about going to a new place as well....