It seems easy to isolate as we age.  Friends (or you) move away.  Others die and you somehow fail to replace them with new people in your life.  Health issues or feeling exhausted mentally makes pulling back easy.   The end result?  You can be living in the middle of millions of people but also living as if you were on a deserted island.  Having an active social life takes effort on your part and it also takes a willingness to change the type of activity you do or the people you let enter your life.  It also seems as we isolate, we get more rigid in our beliefs and opinions so that we tend to drive away the few people who may be left without even realizing what we're doing to the relationship.  Perhaps this is a basic instinct of going back to how we came into the world - by ourselves, but I don't think it's necessarily the best way to head into our "golden" years.  I've known people who have always been greatly involved with life, who have exuded passion and enthusiasm in facing each day, who throw open the door and welcome whatever may come.  I think the choice is ours - if we just recognize that we do have that choice.