Analysis of Sonnet XVIII

THe rolling wheele that runneth often round,
The hardest steele in tract of time doth teare:
and drizling drops that often doe redound,
the firmest flint doth in continuance weare.
Yet cannot I with many a dropping teare,
and long intreaty soften her hard hart:
that she will once vouchsafe my plaint to heare,
or looke with pitty on my payneful smart.
But when I pleade, she bids me play my part,
and when I weep, she sayes teares are but water:
and when I sigh, she sayes I know the art,
and when I waile she turnes hir selfe to laughter.
So doe I weepe, and wayle, and pleade in vaine,
whiles she as steele and flint doth still remayne.