The below link is a wonderfully written, practical article on how to teach our children to be more mindful. We can use it on ourselves as well!
It explains that how by helping your child to pause, you will help them notice what is happening outside as well as inside themselves. Finding this pause will allow a child to respond with awareness to a difficult or challenging situation instead of simply reacting. It can help children manage their feelings in more healthy and appropriate ways.
You or your child can practise being more mindful at any time during the day. It only takes a few seconds. Connect to your breath and drop into how you are feeling. Find the pause.