Songwriters tell us that “Sorry” is the hardest word for a human to utter. But in his latest book, renowned executive coach Marshall Goldsmith says that saying sorry is a great approach to improving relationships and moving on to the future.

Apologizing is one of the most powerful and resonant gestures in the human arsenal—almost as powerful as a declaration of love. It’s “I love you,” flipped on its head. If love means, “I care about you and I’m happy about it,” then an apology means, “I hurt you and I’m sorry about it.” Either way, it irrevocably changes the relationship between two people, compelling them to move forward into something new and, perhaps, wonderful together.

The best thing about apologizing is that it forces everyone to let go of the past. In effect, you are saying, “I can’t change the past. All I can say is I’m sorry for what I did wrong. I’m sorry it hurt you. There’s no excuse for it and I will try to do better in the future. I would like your ideas on how I can improve.”

This kind of statement is hard for even the most cold-hearted among us to resist. And when you use it on coworkers, it can dramatically change how they feel about you and themselves.

I saw this played out dramatically when I was coaching a negotiating team trying to mend fences with its company’s most important strategic supplier – one without which the company would have to shut its doors. I called in a favor and asked Bill Ury, one of the world’s leading negotiation consultants, to join a call with my client and give his input. After listening to the situation, Bill paused a moment and said quietly, “Have you tried apologizing for the past?”

I whacked myself on the forehead and thought, “Why didn’t I think of that?”

Sure enough, that simple apology paved the way for a productive conversation between the two sides that eventually led to a workable solution.

Besides a brain cramp, why don’t we apologize more and defend less? What important business relationship could you re-set with a simple apology?