So what is this mindfulness?
It is quite simply paying full, whole-hearted attention. A typical meditation involves paying full attention to the breath as it flows in and out of the body. Focusing on each breath in this way allows you to observe your thoughts as they arise in your mind and, little by little, to let go of struggling with them. You come to the profound understanding that thoughts and feelings (including negative ones) are transient. They come and they go, and ultimately, you have a choice about whether to act on them.
Mindfulness is about observation without criticism and being compassionate with yourself. When unhappiness or stress hovers overhead, rather than taking it all personally, you learn to treat it as if it was a black cloud in the sky, and to observe it with friendly curiosity as it drifts past.