Mindfulness and mental habits

When we practice mindfulness we notice our mental habit and mental pattern. What makes us angry, jealous, greedy, etc.. My question is, when you notice them, do you change it to positive mental quality or just watch it? Someone angry for 'no reason', but actually there is a reason if one keeps the mindfulness. With mindfulness, we realize that the trigger of the anger is for example a certain situation happened yesterday. By realizing this we are no longer angry. Is this also a practice of mindfulness or analyzing? Which one is the correct practice? Thanks all.