mindfulness involves bringing one's awareness back (i.e. from the past or the future) into the present moment. By residing more frequently in the present moment, practitioners begin to see both inner and outer aspects of reality. Inner reality may unfold as one sees that the mind is continually chattering with commentary or judgment. By noticing that the mind is continually making commentary, one has the ability to carefully notice those thoughts, and then decide if those thoughts have value. Those practicing mindfulness realize that "thoughts are just thoughts"; the thoughts themselves have little or no weight. One is free to release a thought ("let it go") when one realizes that the thought may not be concrete reality or absolute truth. Thus, one is free to observe life without getting caught in the commentary. Many "voices" or messages may speak to one within the "vocal" mind. It is important to be aware that the messages one hears during "thinking" may not be accurate or helpful, but rather may be translations of, or departures from truth.
As one more closely observes inner reality, one finds that happiness is not exclusively a quality brought about by a change in outer circumstances, but rather by realizing happiness often starts with loosening and releasing attachment to thoughts, pre-dispositions, and "scripts"; thereby releasing "automatic" reactions toward pleasant and unpleasant situations or feelings.
However, mindfulness does not have to be constrained to a formal meditation session. Mindfulness is an activity that can be done at any time; it does not require sitting, or even focusing on the breath, but rather is done by bringing the mind to focus on what is happening in the present moment, while simply noticing the mind's usual "commentary". One can be mindful of the sensations in one's feet while walking, of the sound of the wind in the trees, or the feeling of soapy water while doing dishes. One can also be mindful of the mind's commentary: "I wish I didn't have to walk any further, I like the sound of the leaves rustling, I wish washing dishes wasn't so boring and the soap wasn't drying out my skin", etc. Once we have noticed the mind's running commentary, we have the freedom to release those judgments: "washing dishes: boring" may become "washing dishes: washing dishes". In this example, one may see that washing does not have to be judged "boring"; washing dishes is only a process of coordinating dishes with soap and water. Any activity done mindfully is a form of meditation, and mindfulness is possible practically all the time.