Stephen Maturin in "Post Captain"

To my surprise, I've reached a point in Post Captain where I find Stephen distinctly unsympathetic.  It's when he reflects on Diana's aging:

But if, as she says, her face is her fortune, then she is no longer Croesus; her wealth is diminishing; it will continue to diminish, by her standard, and even before her fatal thirtieth year it may reach a level at which I am no longer an object of contempt. That, at all events, is my only hope; and hope I must.  (O'Brian 288)

He does recognize that he may bear some culpability for the vulgarity he has started to see in her features, that "[i]n a relationship of this kind each makes the other, to some extent."