In the opening poem of his sonnet sequence titled Astrophil and Stella, Sir Philip Sidney is already beginning his depiction of Astrophil as a foolish young man who has trouble controlling his selfish desires for the beautiful and virtuous Stella.  In the first poem, Astrophil is presented as a typical “Petrarchan” lover (that is, modeled on the lover depicted by Francesco Petrarca in his own sequence of poems titled Rima Sparse, or “scattered rhymes”). Astrophil confesses that by seeking to make Stella feel sorry for the emotional suffering she is causing him, he hoped eventually to win her love.  He therefore

. . . sought fit words to paint the blackest face of woe,

Studying inventions fine, her wits to entertain,

Oft turning others' leaves, to see if thence would flow

Some fresh and fruitful showers upon my sun-burned brain.

In  other words, he tried to think of appropriate language (“fit words”) in order to make himself seem to be suffering horribly (that is, in order “to paint the blackest face of woe”). He read the fine inventions (the successful writings) of other authors in order to appeal to Stella’s intelligence and cleverness (that is, in order to entertain her “wits”).  He found himself frequently turning the pages of books written by others (“Oft turning others’ leaves”), in order to determine if doing this kind of reading would give him ideas for his own writing. He compares his hope for these ideas to the hope one might have for refreshing, stimulating rain (“fresh and fruitful showers”) during a period of drought caused by excessive heat. 

Astrophil’s reference to his “sun-burned brain” is an especially good example of the way Sidney is already beginning to mock his alter ego. It is almost as if Astrophil, desperate with desire for Stella, feels like a man whose ability to think clearly has been damaged by being exposed too long to the damaging rays of the sun.