kindness

I want to write something about kindness, but although I know what kindness is when I am with children, what is it exactly...
It's something I like to search in children when we work at an art project. I like to relate to the children and after a few weeks I like it when a child that was 'difficult' slowly changes to become more attentive, quiet, smiling, concentrated, kind. When we work together at arts this often happens. We talk, ask questions, work together, share ideas, smile.