You will find that as time moves on your context changes. One day you realise you are talking to your new friends in a way that is more fluid and filled less with explanations to make sense of your world. On the other hand you will find that conversations with friends and family back home may become more challenged. You will start talking about something totally normal for your new life but it sounds totally inappropriate for your old one. It is an emotional time. This is normal, you just need to adjust your language and perhaps be selective about what you talk about, or be aware of how things may sound when said out loud.
It is natural that as time flows by you lose touch with people and you may find you have less and less in common. That is part of life. Yes it can be sad but relationships are a two way street. You will naturally put the effort into the relationships that are the most meaningful to you. At the same time sometimes you need to recognize when you are putting in perhaps too much energy when the other person is letting go. Grieve, celebrate what you have had in that relationship and move on. I really believe that people come into our lives at certain times because we both need something from each other in that moment. Some friends stay friends forever no matter what, no matter how little talk you have through the seasons. There are other friends who do slip away. Who knows, maybe one day we will reconnect. I also have really dear friends and what we have in common are our values, we share a sense of humor and have some common interests. That is enough to keep us going. Even if it is just sending funny messages to each other every few days. That for us, is how we stay connected until we get to have big long and heartfelt chats.
In the expat world you soon get used to saying goodbye and relationships you felt were meaningful become just memories. It is probably only a special few you will remain in contact with after you leave. Expat life is transient and that can be another challenge. Searching through your emotional database to find the manual on how to deal with the emotional rollercoaster of expat life will leave you a little empty handed. I know when I first started to say good-bye I felt such conflict. I really came to understand why some long term expats close themselves off to meeting new people. I will never to that, rather I work through my emotions at the time and keep moving forward. I dread the day however, when my dearest friends here, and I, are separated.