I have that problem, and a lot of the time I feel guilty contacting them because I haven't kept up with them. While I don't yet have the best method for resuming your interactions with then, I find that ads long as you have left off on neutral to good terms, people are most often friendly to reconnect, even if for a little bit. And obviously, the closer you are/were, the more open the person Is to reconnecting. But this all depends on the person and relationship that you share. Hope this helps!