Your own experience is all that counts. Those things that we called hindrances or defilements are more than just unpleasant mental habits. They are the primary manifestations of the ego process itself. This perception is held in place only if it is constantly exercised, and the hindrances constitute that exercise. All the defilements depend upon the perception of a barrier between self and other, and all of them foster this perception every time they are exercised.
Mindfulness perceives things deeply and with great clarity.
It brings our attention to the root of the defilements and lays bare their mechanism. It sees their fruits and their effects upon us. It cannot be fooled. Once you have clearly seen what greed really is and what it really does to you and to others, you just naturally cease to engage in it. There is a reflex action built into the nervous system for just that purpose, and it works faster than thought.