Once the Incense is lit, the process of transmogrification has begun. The Incense immediately begins to take on a different form. This is how & why the Incense has come to represent life itself, as we ourselves are constantly transforming.
As the Incense transcends into an unseen state, lighting Incense has become a way to remind The Self of this principle of Impermanence and Transcendence.
The Incense has come to represent the Sincerity of a person who respects the nature of The Way.