Sincerity by itself and audacity by itself are not necessarily impressive qualities in art. It's possible to recognize that a work is heartfelt without admiring it, and it's possible to recognize the bold churning of imagination without feeling much emotion because of it.
Together, though, sincerity and audacity can be immensely powerful, as in the best-known passage of Christopher Smart's "Jubilate Agno," the lines in which Smart (1722-71) considers his cat, Jeoffry. "Jubilate Agno" was written while Smart was confined in what the 18th century called a "madhouse," and the poem exists in separate fragments. It tends to be the Jeoffry passage of Smart's longer litany (worth reading in full) that finds its way into anthologies—and understandably. The brio and oddball, manic seriousness of the Jeoffry aria are unforgettable.