To My Dear and Loving Husband Love Quotes

How we cite our quotes: (Line)

Quote #4

Thy love is such I can no way repay
The heavens reward thee manifold I pray (9-10)

Why can't the speaker "repay" her husband's love? Isn't her love for her husband a kind of return payment? For a moment here, the husband's love seems just a bit better, or more powerful. For some reason the speaker feels her love for her husband isn't quite up to snuff.