First of all, mindfulness involves paying attention “on purpose”. Mindfulness involves a conscious direction of our awareness. We sometimes (me included) talk about “mindfulness” and “awareness” as if they were interchangeable terms, but that’s not a good habit to get into. I may be aware I’m irritable, but that wouldn’t mean I was being mindful of my irritability. In order to be mindful I have to be purposefully aware of myself, not just vaguely and habitually aware. Knowing that you are eating is not the same as eating mindfully.
Let’s take that example of eating and look at it a bit further. When we are purposefully aware of eating, we are consciously being aware of the process of eating. We’re deliberately noticing the sensations and our responses to those sensations. We’re noticing the mind wandering, and when it does wander we purposefully bring our attention back.
When we’re eating unmindfully we may in theory be aware of what we’re doing, but we’re probably thinking about a hundred and one other things at the same time, and we may also be watching TV, talking, or reading — or even all three! So a very small part of our awareness is absorbed with eating, and we may be only barely aware of the physical sensations and even less aware of our thoughts and emotions.
Because we’re only dimly aware of our thoughts, they wander in an unrestricted way. There’s no conscious attempt to bring our attention back to our eating. There’s no purposefulness.
This purposefulness is a very important part of mindfulness. Having the purpose of staying with our experience, whether that’s the breath, or a particular emotion, or something as simple as eating, means that we are actively shaping the mind.