To me mindfulness is a fancy term for "being in the moment".
I have caught myself doing things and already thinking of the next thing while I'm in the midst of doing. More often than not, I bang my fingers, hand, toe, ankle because I wasn't attending to the present moment. I had already moved on but my body didn't know it so it lost its navigation.
I also find my mind wandering when I'm meditating. This happens to everyone, yes, even enlightened ones. When I notice I've wandered, I gently bring myself back to meditating.
There is no need for recriminations. Awareness will improve with practice.
If I find that I'm reliving a slight, a physical or mental injury or an embarrassment, I bundle it up in my arms and give the bundle to the person or persons involved, handing it back to them. I also do a chopping motion with my hands so that I sever the connection to the bundle.
Free-will allows me to take the bundle back sometimes so I find that I need to hand it back until my heart is truly ready to give it back.