Like a nail, an apology is a small yet fundamental tool. Without it, things fall apart.

According to psychologist and author Harriet Lerner, Ph.D., relationships can fail because someone will not apologize after an argument. Even the best relationships can suffer quietly beneath the surface when something hurtful is done or an insult goes unrepaired.

“I’m sorry” are the two most healing words in the English language. When they are said as a true heartfelt apology, these words can heal a relationship. A good apology can free a person from experiencing constant anger, bitterness and pain.

In Lerner’s book Why Won’t You Apologize, she explains how an apology allows the hurt party to explore the possibilities of healing rather than struggling to make sense of the pain and the other party’s words or actions.

The most difficult part of apologizing is getting it right. It requires courage and understanding. “The wisdom to do it wisely and well is at the heart of effective leadership, coupledom, parenting, friendship, personal integrity and love,” says Lerner. “It’s hard to imagine what matters more than that.”

More Insight: Maybe a little stressed out? Check out this article!