Mutability by Percy Bysshe Shelley

Even though the poem begins pessimistically there is an ironic change in the way Shelley views mutability.
On one hand, because we as humans mutate and change we eventually, like clouds, disappear.
On the other hand, we are all individuals, even though we may be forgotten, we are unique. There is no replica.
Even when we rest (sleep) there is no constancy because of dreams. When we are awake, one thought leads to another, in this way our thoughts are always shifting. Each change in emotion signifies a shift.
Each day wears on and soon is replaced by the next.
The only thing that remains constant, as Plato said it a long time ago, is change.
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