In "A Defence of Poetry,” Shelley suggests that emotions experienced in life are constantly changing. Which lines from "Mutability” can also be seen as a reflection of this idea?

Streaking the darkness radiantly!—yet soon
Night closes round, and they are lost for ever
We rest.—A dream has power to poison sleep;
We rise.—One wandering thought pollutes the day
We feel, conceive or reason, laugh or weep;
Embrace fond woe, or cast our cares away
Man’s yesterday may ne’er be like his morrow;
Nought may endure but Mutability.