"Mat chats" are very, very common in children's martial arts programs. We all know that character development is a big reason why parents enroll their kids in martial arts classes. Doing a "mat chat" to tell the kids, you know, "don't hit your classmates, clean your room, listen to your parents" etc and so forth is one way to teach character development.
I do a little bit of that with my Little Dragons, particularly to emphasize that they should only ever kick or punch someone when they're at the martial arts school wearing their special sparring gear so nobody gets hurt, that they should never hit their mom or dad or siblings, that it's important to take turns and help each other out, etc. I'd like to incorporate some more of that kind of thing (i.e. maybe talking to them about dealing with feelings, like if you get angry to count to ten and take deep breaths, etc), and I've been reading some preschool child development books to get some ideas, but I've been struggling a little with the best way to approach it in this context.