Accuse me of betraying your love through distraction and infidelity; I boast of these failings only to test whether your constancy will survive proof of my unworthiness.
The speaker catalogs his infidelities: he's 'scanted' the beloved's deserts, forgotten to repay them, been 'frequent with unknown minds,' given away the beloved's 'dear-purchased right,' and sailed toward distant horizons. Yet these are presented as deliberate provocations, not genuine betrayals. The speaker is testing whether the beloved will remain constant despite provocation—a dangerous and manipulative strategy dressed up as penitence.
Lines 9-12 ask the beloved to 'book' the speaker's willfulness but 'shoot not' in wakened hate. The speaker simultaneously invites judgment and begs to avoid it. This contradiction is resolved by the couplet's claim: the speaker was 'striving to prove / The constancy and virtue of your love.' The transgressions were designed to test the beloved's love—a rhetorical strategy that frames infidelity as devotion.
You've been distant, hung out with other people, neglected them. Now you're saying: go ahead, be angry at me, test whether you actually love me or just the idea of me. It's a confessional designed to prove something.