Every romantic relationship has an Original Agreement—be it sexual, financial, emotional, or a combination of all three. And when this Original Agreement isn't being fulfilled, it causes the relationship to stall, or end. Although there are plenty of exceptions, statistically this happens most in new relationships, and it seems to be the woman that breaks things off for a number of reasons. If it's really that early in the relationship, the reasons are usually big... "dealbreakers" of a sort: Lying, cheating, financial infidelity. The million-dollar question: After this kind of break-up, why do exes come back, or get in contact after some time has passed?

From an anonymous female reader:

"I had a relationship that ended very badly (after I discovered him lying about some things), and I told him to never contact me again. And he respected my wishes — until yesterday. Out of the blue I received a well-wishing text. I've always said that exes are like boomerangs, but I never in a million years thought this ex would reach out to me again for any reason — especially because I shamed him once he confessed to everything that was going on. What gives?"

People learn from their mistakes, but not as quickly as others would hope. But why do they return, especially after horrific break-ups? There are a few possibilities:

Epic Sex. No one wants to give up good sex. If there was a good physical relationship, it's a good reason for them to return... especially if they know that you enjoyed the sex, too; that's their "in" (so to speak).
The Do-Over. When it comes to relationships, many people are experiential learners, and they learn more by making mistakes. After they've made a few, they end up altering their behavior and patterns, and then move on to their next relationship — presumably more prepared. If they made a bunch of mistakes with a past partner, yet felt that there was some kind of connection, they may return for a second go-round. Note, however, that relationship dynamics tend to stay the same, even on a second try. Unless both people have changed as individuals, you may repeat the past. After all, when you pull milk out of the 'fridge and it's spoiled, you don't put it back and hope it's fresh tomorrow. Sometimes, you just have to throw it out.
Single... again. Men and women on the rebound tend to reconnect with past lovers. The reasons vary, but mostly due to the above mentions motivations. By reaching out with a simple phone call, email or text message, they're testing the waters and will gauge what is possible by the reaction.

So, do you go back with an ex?
Before striking back up with an ex, consider the following:

You can't "go back" to an old relationship... unless you want the same results. Going back to an ex means you will start a new relationship with someone from your past. You have to release what you think you know and get to know them all over again.
Don't jump into bed right away... especially if the sex was incredible. You'll risk repeating your old relationship by fooling yourself about the level of connection.
Don't focus on the past... unless you are reminiscing about good times. Past disagreements (or what broke you up) can be discussed... but then you need to leave it alone.
Above all... take your time. Let the new relationship reveal its own possibilities, and you'll see what's possible.