From what I know so far mindfulness is about being in the present moment, not thinking about what your gonna do or should do just living purely on the present. I have a memory from a while ago where me and some friends had just been paintballing and we were on the bus home. I remember being covered in mud and uncomfortable in my clothes cause of it but the sun was setting, I was surrounded by a bunch of my friends all being rowdy and having fun and in that moment I consciously preserve the memory because I was so happy and thankful to be alive. I think in that moment I was being truly mindful.
Now knowing more about mindfulness I know that a time when I'm also very mindful is when I'm doing a task that requires a good amount of focus that I also take seriously e.g. playing basketball or being in the gym. I'm also mindful whilst gaming but only when I'm playing competitive or doing particularly good. This makes me think that, in a way, I'm not taking most of life seriously cause when I'm taking something seriously I give it all of my attention and am very mindful. Anyways, I do now know what mindfulness is and how to start implementing it into my life and that's exactly what Im going to do.