Mindfulness means paying attention in a particular way: on purpose, in the present moment, and nonjudgmentally (Jon Kabat-Zinn).
We can only be mindful in the here and now, but where are we most of the time? Usually lost in our thoughts, traveling mentally between past and future.
Remembering that the present moment is all we have can lead to a more balanced way of looking at life, more acceptance, and better mental health.