How do we go about destroying the root cause of samsara now that we have identified it? Will burning incense, doing prostrations and reciting mantras work? They may, to some extent, if performed with genuine renunciation and bodhicitta. Renunciation can help us deal with the more observable defilements while the subtle ones can be subdued by relative bodhicitta. However, the subtlest self-grasping can only be eradicated by the practice of not-self and emptiness, hence their inclusion in the four characteristics. As for impermanence and suffering, why are they part of the four characteristics? They are appointed so as to help us form an aversion to samsara and thereby stop all worldly pursuits.
[Excerpt from Luminous Wisdom Book Series 1: The Right View ~ The Four Noble Truths]