How can paying attention to brushing my teeth help me? Isn't it better if I use that time for planning my day?

Most of us have spent years practicing this habit of not paying attention to our lives as they are unfolding. So, the bigger picture is that you are learning to shift from a habit of continually projecting into the future or ruminating about the past, to a habit of being aware of what's really happening now. Training the attention to stay with experience as it is occurring supports the mind's ability to see things clearly and learn. We begin to see what truly is present, not what we wish or fear is present; we begin to interact with experience as it is, not colored by our habitual "filters" or automatic views. We begin to unravel our struggles with experience, and in doing so, are better able to respond in daily life to whatever comes up with creativity and heart. And so, when it's time to plan your day, you can really be there, with all your capabilities, for planning your day.