Whether you're negotiating with your boss, landlord, roommate, colleague, or spouse, knowing what to say and how to say it is invaluable.

Because in essence, life is a series of negotiations. Whether you're negotiating for a higher salary, a lower price on that new car, a long weekend away with your loved one, or for your child to do her homework, the difference between a successful negotiation and a failed one has real repercussions on your life.

Chris Voss, former lead international kidnapping investigator for the FBI, has some valuable advice on the subject.

Voss started his career as a policeman in Kansas City, Missouri, of all places. He then joined the FBI, where he rose in the ranks, first as a hostage negotiator and eventually as lead international kidnapping negotiator. In his work, he regularly came face-to-face with terrorists, bank robbers, and more.

You might think successful negotiation is all about cold calculations and forceful manipulation, especially in high-stakes circumstances like hostage situations. However, it turns out skillful negotiating is far more about emotional intelligence than it is about attempting to coerce the other person into doing it your way.

In other words, most people believe that when it comes to persuading someone else to do something, you need to make them agree with you. But according to Voss, what you should do instead is actually show them that you see them.

That you hear them.

In fact, according to Voss, one of the most powerful phrases you can hear from whoever you're negotiating with is:

"That's right."

Not "You're right." But "That's right."

Why? Because if they say to you "That's right," it means you've outlined their perspective or point well enough that they agree with you. They're backing up your assertion, letting you know you've nailed it.

According to Voss, reaching this point of understanding is "revelatory in the art of negotiating."

He's also clear that making sure the other party feels heard is not just a touchy-feely strategy. "Psychotherapy research shows that when individuals feel listened to, they tend to listen to themselves more carefully and to openly evaluate and clarify their own thoughts and feelings," he says.

In other words, when someone feels listened to, they can even change their own mind--without you having to do a single thing.

In Voss's book Never Split the Difference: Negotiating as if Your Life Depended on It, he outlines nine effective principles of negotiation. They're all different, but share a core notion: that genuinely empathizing with the other party is a critical element of persuasion.

"The beauty of empathy is that it doesn't demand that you agree with the other person's ideas," says Voss. This vital negotiation skill isn't about agreeing; it's simply about understanding.

Nelson Mandela spent 27 years in prison. While behind bars, he spent significant time and energy researching the Afrikaners. He wanted to understand them, see where they were coming from. He knew that the more he could get inside their heads and truly grasp their perspective, the more he'd be able to communicate with them--and possibly come to an agreement.

Of course he didn't agree with apartheid. But he knew that the more his opponents felt heard, the better he could negotiate with them--and achieve his goal: freedom for millions.

"Negotiate in their world," says Voss. "Persuasion is not about how bright or smooth or forceful you are. It's about the other party convincing themselves that the solution you want is their own idea. So don't beat them with logic or brute force. Ask them questions that open paths to your goals. It's not about you."

It's not about you.

It's about listening. And a good way to know whether the other party really feels heard is to listen for that magical two-word phrase:

"That's right."

Most people go into a negotiation with their own desire front and center. They don't go in actually wanting to know how the other person feels and what they want, and why.