Relational mobility means having different relationships with different people. It's like having a lot of different friends that you get along with really well, but each friend "specializes" in something different. For example, one friend is really good at music and teaches you songs, another friend is really good at sports and plays a lot of sports with you, and another friend is really good at art and teaches you how to draw. Relational mobility means having a lot of different friends and not just focusing on one relationship all the time.