Mattie's poetry is full of what he calls "heartsongs."
"A heartsong doesn't have to be a song in your heart. It doesn't have to be talking about love and peace. It can just be your message. It can be your feeling," he says. "Some people might even call it a conscience, even though that's not really what it is. It's your message, what you feel like you need to do."
Everyone has a heartsong, Mattie says. "No matter what it is, it still sings the same beautiful message of peace and love. People are fighting over how our heartsongs are different. But they don't need to be the same," Mattie says. "That's the beauty. We are a mosaic of gifts. Each of us has our inner beauty no matter how we look."