Let me just start this be saying the following: as a species, humans find it really tricky to maintain relationships with another being. Friendships, relationships, marriages, divorces, and everything in between —
Consider this a tough-love approach, but I've said this to friends and family too many times to not say it here: if you keep knocking on the devil's door long enough – sooner or later somebody's going to answer you. What do I mean by that? It's rather simple really, with exceptions obviously because not all break ups are the same. If you are still "friends" with someone or connected in some way on social media
And there's nothing wrong with that feeling. You are allowed to grieve and mourn the loss of something that you held so near and dear. However, social media is very tempting in the sense of having access to all the information —
Allow yourself to heal and take care "Me, Myself, and I" to heart. Depending on the circumstances, there's absolutely a whole host of reasons where anyone will just say "delete" them from your life and begin anew. Domestic violence, cheating, physical and emotional abuse, or even worse. That level of negativity never was necessary in your life; and sure as hell isn't needed if that person is no longer involved. Yet, if it's been some years, and you have way too many mutual friends, then perhaps you can be cordial through a computer screen and leave them be. Hide them from your newsfeed, mute them on Twitter, do whatever you have to do to maintain a safe distance if that is what you truly need to do.
I guess the bigger point that I am trying to emphasize is that before you can begin to be with someone else, you have to learn, love, and understand yourself. This is especially true if you've got some emotional healing and growing to do (don't we all) before you put that Match.com profile up and hope a new fish bites. I know there's nothing like seeing that all of your mutual friends and your ex did something without you, with a whole bunch of likes and Instagram hearts, but with time, you too will be out and out, and not worrying about FOMO.