For me, mindfulness is like water. It erodes the toughest rocks yet is essential for life. Mindfulness is accepting that fact. It's observing and experiencing in the neutral zone.

A good example of it being used (and silly) was when my TA explained his getting a speeding ticket.

There are streetlights that have cameras on them, and he got caught for speeding. They had someone serve him. Basically, a nice looking older lady gave him his tickets and told him he would have to go to court + fee or take drivers ed. He was upset at the lady for giving him the ticket, but this wouldn't have happened if he hadn't sped in the first place. He ended up doing drivers ed online. Mindfulness allows you to let go of your emotions tied to the situation and look at it from a neutral point of view. He was also able to relinquish the anger he had towards himself for speeding and got over the fact that he was served.

This situation is silly, but it can be applied to many things in life. It opens you to critiques which allows you to better yourself. It also allows you to remove your emotions from things in the past and see them for what they were. This allows you to be more open to critiques and discussion about what happened so you're more willing to work on it.

Disclaimer: This is what mindfulness means to me