To Lucasta, Going to the Wars Love Quotes Page 2

The speaker offers a strange paradox here: he claims that Lucasta will "adore" his betrayal, his inability to stay with her. The lines imply, perhaps, that true love is able to endure disappointment and inconstancy, even though we might not expect it to be able to do so.

What's with all the negatives here? (As in "could not" and "Loved I not.") Can the speaker not positively describe his love?