The brain has the capacity to experience many things simultaneously. Although, meditation and mindfulness make us realize that the mind can only be aware of one thing at a time. As you are reading this paragraph there are sounds around you but you cannot hear them at the same time you are reading these words. What makes you think that you can be aware of sounds and see these words at the same time is simply the speed at which the mind alternates from hearing to seeing. This is probably where the notion of impermanence reaches its most liberating aspect. Developing mindfulness allows us to experience one thing at a time and thus avoid the destructive aspects of switching from thoughts to body sensations without noticing it. We can realize how powerful mindfulness is, this capacity to put the mind where we want and to stay on that object instead of very quickly changing the focus of the mind without being aware of it. It leads to a state of contentment and concentration, a great source of happiness.