Like as, to make our appetite more keen,
With eager compounds we our palate urge;
As, to prevent our maladies unseen,
We sicken to shun sickness when we purge;
Even so, being full of your ne’er-cloying sweetness,
To bitter sauces did I frame my feeding;
And, sick of welfare, found a kind of meetness
To be diseas’d, ere that there was true needing.
Thus policy in love, to anticipate
The ills that were not, grew to faults assur’d,
And brought to medicine a healthful state
Which, rank of goodness, would by ill be cur’d;
But thence I learn and find the lesson true,
Drugs poison him that so fell sick of you.
In plain English
The speaker compares himself to someone who deliberately makes himself sick — either by forcing strong spices on his palate to sharpen his hunger, or by purging himself to prevent imaginary diseases. He did something similar in love: drowning in the fair youth's sweetness, he deliberately went looking for bitter experiences, seeking out infidelity or coldness as if inoculating himself against future pain.
This was a calculated move, trying to get ahead of heartbreak by breaking his own heart first. But the plan backfired. He poisoned a healthy love by introducing sickness into it — like using toxic medicine on someone who was never actually ill. Now he understands the hard lesson: trying to protect yourself from this person through deliberate unfaithfulness only destroys you.
