Mindfulness Meditation is a practice of being fully and attentively present in the moment. In the same way one might practice a musical instrument or martial arts form, we practice being mindful and aware through skillful meditation. In formal practice we use the breath as an object of awareness. We follow the physical sensations of the breath as it flows in and out of the body. We allow the breath to flow naturally without controlling it as you would in a breathing exercise. We simply hold the sensation of breath in our field of awareness.
One of the first things we learn when we try to do this practice is how easily distracted the mind can be. All sorts of thoughts, ideas, feelings, and sensations call for our attention and we find we have forgotten all about the breath. When we realize that we have been distracted, the appropriate response is to simply return to awareness of the breath with kindness, gentleness, patience, and a little dose of curiosity about ourselves.
As with any new skill, this becomes a little easier each time and develops best if we set aside any self-conscious judgments or expectations about how our meditation is developing. The practice is to simply relax and wake up to the awareness of what is happening in the present.