A while back I asked for advice on how to overcome the dreaded oneitis. The overwhelming responses were something along the lines of "move on" or "just get over her". As a result of many months ( yeah I thought she was that cool ) I did succeed in getting over her. And what I learned was to distinguish between love and lust. I found stepping back, and looking at your situation objectively, can allow you to see things from the outside looking in.

For example, you know exactly if a girl/guy is bad for your friends when looking from the outside. If you find yourself obsessing just a tad, force yourself to look at it from the outside. That helped me at least and I'm just trying to help :D.

TL;DR step back, breath, and view oneitis as if you were viewing a friend in a similar situation.