Sonnet 90 is the third of three poems that form a 'group within a group', purporting to accept, even support, any decision the young man may wish to take to leave his poet lover, for whatever reason he deems justified.

Its principal message is straightforward: if you are going to leave me, then do it now, while everything else is going against me anyway; and with this emphasis on what 'now' is like for William Shakespeare, it sheds a fairly powerful light on Shakespeare's position – or at the very least on how he perceives his position – as he writes this sonnet and the ones that accompany it.