In my pov, this thread is about
when you're the one who's two timing, you'll be the most lonely one, because you'll know who you'll want, and all. The story plot is in your hand and there's nothing much you can do except to wait for the other two parties to do onto you.
You may feel a moment of happiness, a moment of satisfaction(that you can have 2 at one go), but as time goes by, this fade and nothing will matter anymore.
Your partner won't know; the other person may jus be hurt and get over it.
At the end of day, you will only have two endings - Lose both or seek forgiveness from either one.
Aren't this lonely and tormenting eventually?