Breaking up with someone is hard.

Sure, we all know that. Sometimes the hardest part is recognizing when the relationship has gone sour.

What’s the difference between simply losing the newness and the relationship running its course?

I’m not usually one to buy those “how to” dating books, but I heard so much hype about Greg Behrendt and Liz Tuccillo’s “He’s Just Not That Into You,” that I decided to buy it. I mean, this guy was on “Oprah.” The book must be somewhat insightful.

A writer and a consultant of “Sex and the City,” he goes through letters from women who describe their less-than-perfect relationships, citing their man’s fault. Behrendt uses blunt words to slap them upside the head and tells them to dump the unworthy guy, plain and simple. Many relationships may have ended as a result of this book. It was that liberating “you deserve better” book.

Many of the situations make you think, “Yeah, I’ve dated this guy.” This is common sense. Do people really need a book to tell them their main squeeze doesn’t want them?

Most of the time, yes.

If you walk in your apartment and he’s under the sheets with your roommate, it might be a pretty good indication he doesn’t like you all that much.

But we do need to be told this sometimes, maybe not by a book, but by our friends.

Why do you have to be on the outside looking in to recognize your other half’s flaws? Because you’re really into them?

Not always. We don’t always believe it’s possible for someone to not want to be with us.

In a Behrendt-style poll taken, 100 percent of guys said they don’t ignore a girl they like. No? So I guess he doesn’t like me, huh? Why didn’t I see this before? I thought he was playing hard to get. Ah, well. I will continue to sit next to him in sociology class and slip photos under his door of his head pasted over my ex’s head.

Getting the hint can take a while for some people. Ignoring them, belittling them or blowing them off doesn’t always work.

Remember, no one likes a clinger and no one likes to waste time. So stop pasting heads onto photos and find someone who will physically stand next to you for once.