Analysis of Sonnet 153: Cupid laid by his brand and fell asleep

Cupid laid by his brand and fell asleep,
A maid of Dian's this advantage found,
And his love-kindling fire did quickly steep
In a cold valley-fountain of that ground;
Which borrowed from this holy fire of Love
A dateless lively heat still to endure,
And grew a seeting bath, which yet men prove
Against strange maladies a sovereign cure.
But at my mistress' eye Love's brand new-fired,
The boy for trial needs would touch my breast;
I, sick withal, the help of bath desired,
And thither hied a sad distempered guest,
    But found no cure. The bath for my help lies
    Where Cupid got new fire—my mistress' eyes.