As the famous "This American Life" episode about breakups notes, breaking up with someone is an incredibly common thing. Almost all of us have gone through it, maybe even multiple times. You go through phases of misery and crying and anger and despondency, and even as you are experiencing these emotions, you know that it's all kind of a cliche. But as the guest on TAL says, "When it happens to you, it feels so specific."

And you can talk for hours and hours (even days, I'll admit I have!) about why you broke up with someone, but in the end it's usually for a simple reason: one or both of you fell out of love. But how does that happen?

1. Mistaking lust for love. It's a bit of a bummer, but it's almost impossible to stay as madly lustful for someone as most of us are in the first few months of a relationship. Oftentimes (usually young people) think this state of zealous infatuation is supposed to exist forever, and when it doesn't, they think they've fallen out of love. But the thing about relationships is that, over time, they change. You might have less fiery sex, but it's likely to be deeper and more romantic (dare I say better) than in the early days. And of course, relationships aren't all about sex, and sex doesn't equal love.

2. Forgetting how great your partner is. By focusing on the things they do that irritate and annoy you, it's actually easy to forget that you love them. Work out your frustrations, sure, but don't forget to notice the things about your partner that you love and appreciate. (And tell them about it.)

3. Holding grudges. Being angry with the one you love sometimes is perfectly normal, but holding a grudge for something that you have talked about and they've apologized for or you've worked out is a recipe for disaster. It will stop you from loving them fully, so let it go. If it's truly an unresolved issue, talk about it again, or try writing about your feelings. But if an issue is past and done and you're still thinking about it, it will poison your relationship and lead to either you falling out of love with them or vice versa. Nobody can sustain a loving relationship with someone who won't forgive — and this includes forgiving yourself for wrongs you may have committed. At a certain point, you must let things go and move forward.

4. Incompatibility. The first few months of a relationship can fool you into thinking that you get along with someone better than you really do. But over time, real differences emerge. That usually means that as time goes by and you see the truth, less fogged by passion, you feel less love for the person. It's sad, but also a very good reason to break up with someone. If you really want different things for your futures or your day-to-day lives — or attitudes about money, kids or sex are too different — that's a deal breaker.

5. Dishonesty. Nothing makes someone fall out of love faster than feeling lied to or betrayed. If you want to see someone fall out of love with you in minutes, watch what happens when they catch you in a lie. Telling the truth can be difficult, but it's part of being in a loving relationship. Be honest and expect honesty in return. Just remember that you won't always like what you hear, and that's OK.

All of this considered, there's something inexplicable about being with someone you love and then breaking up. Knowing the reason why you or they fell out of love isn't likely to make you feel better in the moment, but over time it can offer some solace.

"I felt her absence. It was like waking up one day with no teeth in your mouth. You wouldn't need to run to the mirror to know they were gone," writes Gunnar Ardelius in "I Need You More Than I Love You and I Love You to Bits." And that's exactly what it is like when you have lost your love.

Starre Vartan ( @ecochickie ) covers conscious consumption, health and science as she travels the world exploring new cultures and ideas.

5 sadly common reasons people fall out of love
It's sad, but it happens to the best of us. Sometimes, the love just dies.