How does the structure of this italian sonnet by petrarch support its theme?

those eyes, 'neath which my passionate rapture rose,
the arms, hands, feet, the beauty that erewhile
could my own soul from its own self beguile,
and in a separate world of dreams enclose,
the hair's bright tresses, full of golden glows,
and the soft lightning of the angelic smile
that changed this earth to some celestial isle,
are now but dust, poor dust, that nothing knows.
and yet i live! myself i grieve and scorn,
left dark without the light i loved in vain,
adrift in tempest on a bark forlorn;
dead is the source of all my amorous strain,
dry is the channel of my thoughts outworn,
and my sad harp can sound but notes of pain.