Qin Cha Bai Juyi, what role do the first two sentences of the poem play in the whole poem?

A sentence or two always begins with a poem. The first sentence explained the reason for his resignation, because his aloof temperament was contrary to the atmosphere of officialdom. (2) The second sentence explains the cheerful nature. (3) These two sentences express their feelings directly, which leads to Ersanlian's description of the leisurely and elegant life after resigning; Echoing with the tail couplet, it paves the way for expressing the feelings of loyalty to the court and courage.