Mom's viral apple post is the perfect way to show kids how words can hurt

Her post about apples and kindness first went viral four years ago, but U.K. mom Rosie Dutton said it's every bit as relevant today.

That's why she decided to re-share the post to her Facebook page Mum in the Moment earlier this week.

"I'm extremely passionate about children's mental health and well being and run relaxation and mindfulness classes for children and families," she told "Good Morning America."

The apple lesson, as she calls it, is one of the ways she teaches children about kindness.

"I knew from my own childhood that words can hurt, but that we don't often show the pain on the outside," she said. "We can go for years or our whole life hiding it. This visual demonstration using the apples always makes people think."

It goes like this: Prior to the lesson, Dutton drops one of two apples repeatedly on the floor, but it still looks just like the other on the outside.The kids don't know this and are presented with two identical apples. She then has the children speak mean words to the apple she dropped and kind words to the one she did not.

Then they cut both apples open.

Her post reads in part, "I think there was a light bulb moment for the children immediately. They really got it, what we saw inside that apple, the bruises, the mush and the broken bits is what is happening inside every one of us when someone mistreats us with their words or actions."

The lesson is needed now more than ever, Dutton told "GMA."

"The way we treat each other and the way we speak to each other online and in life makes a huge difference to our happiness and mental health," she added. "You never know what someone is going through so our words matter."

Since the post went viral, she's learned "so many people really value kindness. In all the comments and shares the post still gets people talk about how kindness matters, how it makes a difference, how it makes them feel."

After all, she said, "Kindness never goes out of date."