What a great question.
I will try to explain what mindfulness means to me.

Paying attention to my body did seem very strange at first.
I have spent so many years ignoring my emotions and physical sensations.

With the help of my therapist I am learning that I am not my emotions or my thoughts.
The first step for me is noticing my physical and emotional states and accepting them as I am (a long time ago there was a very good reason to protect myself with numbness), and being able to ask myself is this 'reality now' is this 'helping me', so now I have a choice. Do I go with the automatic reflex or is there another reflective way?

When I am really anxious I can try with mindful breathing to lower my level of anxiety. Even if I lower my anxiety for just a few seconds, this does help, the hard part is remembering that I can use my breath to create a change in my body.
Then my mind can say 'oh look the body is not stressed so the danger is passed'. This is in some sort of neurotranmitter hormone brain body language.
After reading what I have written I realized I am not sure if I understand what mindfulness really means.

This will be a lifelong practice and most importantly to practice mindfulness when I'm not anxious or stressed. I do not want to associate anxiety with mindfulness.
Quite often I can't identify what is causing the stress then if I remember to take a few deeper breaths I can relax enough to think.
Finally after three years of trying to be mindful I think I'm starting to feel the positive results. (treatment resistant depression)
There are lots of videos online where you can learn about and practice mindfulness. With people that know what they are talking about.

G1