The most prominent feature of this poem is that the poet embodies emotions in things. Flowers bloom and fall, swallows fly, and Zigui cries at night, all of which are natural phenomena. However, the poet believes that flowers, swallows and birds are all doing this to call back the dying spring. Spring has not passed away, but life still exists.
Zi Gui has been crowing, but if you don't believe it, you can't call back the withered spring. In the last two sentences, the poet expressed his firm belief, optimistic spirit and persistent pursuit of a better future, showing his firm confidence.