You see your own selfish behavior. You see your own suffering. And you see how you create that suffering. You see how you hurt others. You pierce right through the layer of lies that you normally tell yourself and you see what is really there.
Mindfulness leads to wisdom.
Mindfulness is not trying to achieve anything. It is just looking. Therefore, desire and aversion are not involved. Competition and struggle for achievement have no place in the process. Mindfulness does not aim at anything.