You can do better. It started one night when we realized that we were both pining over the respective guys that we were seeing (or maybe more accurately, trying to see) and evaluating our own behavior towards them, asking what we could have, should have, would have done differently.
Then we realized that we could have, should have, would have done nothing. If the way these men were treating us was making us unhappy, then why should we be questioning ourselves? And "You can do better" was born.
We realized that if someone's behavior is a source of unhappiness or discontent, then not only would we be unable to change the person to make us happier, but it wouldn't even be worth the effort! So we made a list of everything that made us unhappy, everything that we should not allow ourselves to settle for, and said that if someone we were seeing belonged on the list, then we could do better. Sometimes it's funny, sometimes it's heartbreaking, but it's always true. And once it was written down, it was like a big dose of reality and empowerment rolled into one.
The purpose of "You can do better" is not to set impossible standards or refuse to compromise. "You can do better" is about not compromising respect and fulfillment. It doesn't matter if he's into you or not, but if he can't pull it together for you, then you can do better!
If he breaks up with you because "he's not ready and it wouldn't be fair" and then turns around and dates other people, then you can do better!
If, after you hook up, he recounts graphic details of his various threesomes, then you can do better!
If he tells you he doesn't think he can ever marry you because you're not into Metallica, then you can do better!
If he buys your drinks but texts you two days later to say that you owe him for it, then you can do better!
If he starts dating two Russian prostitutes immediately after breaking up with you, then you can do better!
If he thinks that regaling you with stories about playing "Edward Forty-Hands" in college is good conversation, then you can do better!
If he thinks Obama wasn't born in the US, then you can do better!
If he tells you that you "don't know what real pain is" while you are in labor with his child, then you can do better!
(for boys) If she won't let you have a bachelor party, then you can do better!
If he tells you that he has an Asian fetish, and makes moaning sounds when an Asian woman walks by, then you can do better!
If he hits on you via Twitter, then you can do better!
If he only calls you between girlfriends, then you can do better!
If he says that he'll call you once he breaks up with his girlfriend, then you can do better!