“Sonnet 35: No more be griev’d at that which thou hast done” by William Shakespeare

No more be griev’d at that which thou hast done:
Roses have thorns, and silver fountains mud;
Clouds and eclipses stain both moon and sun,
And loathsome canker lives in sweetest bud.
All men make faults, and even I in this,
Authorizing thy trespass with compare,
Myself corrupting, salving thy amiss,
Excusing thy sins more than thy sins are;
For to thy sensual fault I bring in sense—
Thy adverse party is thy advocate—
And ’gainst myself a lawful plea commence:
Such civil war is in my love and hate,
That I an accessary needs must be
To that sweet thief which sourly robs from me.

This is another of the Fair Youth sonnets. In this poem, the speaker is addressing a wrong which the young man committed against him. The sense that I get is that the speaker believes that the youth was not faithful, specifically from line 9…