Most people seem to have more bad dreams early in the night, progressing toward happier ones before awakening, suggesting that they are working through negative feelings generated during the day.
The origins of "Ozymandias" were humble: a playful contest with a friend, Horace Smith, a jolly London poet-stockbroker, who was staying with Shelley at Marlow.
They were then asked if they had felt different affective states (happiness, enjoyment, stress, sadness, anger and worry) "a lot of the day yesterday."
He did this by having them watch movie clips that either invoked happy or sad emotions, and asking them to dwell on positive or negative aspects of their own lives.