The number one reason you shouldn't be overly concerned that your ex is dating someone new is that this is almost certainly a rebound 'fling' for your ex.
He or she hasn't fallen madly in love with someone new, and you haven't been 'replaced' in your ex's mind. A rebound is a way for your ex to take his or her mind off the pain of your breakup while avoiding the loneliness that comes with the single life.
Before you know it, the supposed “official end” of a relationship has no meaning.
If you try to somehow sabatoge their relationsip, you're really killing all hope of ever winning your ex back.
So, for the time being, just take this one on the chin and try to accept it as an unfortunate reality for now.
Most rebound relationships are over in 3-5 weeks, and your ex's rebound will likely be equally short-lived.
Keep in mind that a rebound is not a romantic, love-based relationship.
If you weren’t broken up before, you sure as hell are now.
During your post-breakup period, it was easy to push your limits with your ex, whether it was with those drunken hookups, calling him or her late at night “just to talk,” laughing together at parties or joking about the silly or embarrassing things that happened in your relationship.
That’s when your ex’s focus shifts away from you and to another person.
That’s when the definition of “breakup” is no longer unclear.
Deep down inside, you might have had this weird fantasy that you and your ex would get back together one day.