Today we expand the field of our mindfulness to include all we practiced before - the breath, body sensations, emotions - and now we also include thoughts. We learn to acknowledge a thought and name it, e.g. thinking, planning, worrying etc. This way we learn to be aware there are thoughts, but this doesn't mean that we ARE our thoughts. Also, crucially, we don't have to believe our thoughts. The thought is real, but not necessarily true.