[..... Nods, and doesn't argue it -- and hates that, really, part of him is happy that she would say as much, even as another part of him regrets that he should cause her that pain in the first place, hating that he had to leave her behind at all]
I-- I promise. [And this is a promise he actually intends to keep this time.] [Breathes out, shakily] I have been luckier than most, to have had you for a wife, and to have you by my side for all these years... and-- and I would never look back on those moments with regret. When I think of you... I can only think that I was the luckiest man.
And-- even if, here, there was sadness, too... [he's not going to deny that, isn't going to lie to her] Don't think, Guinevere, that knowing that you are forever in my heart wouldn't also bring me happiness. Whatever becomes of me -- you will always be with me. There will never be a day when you're not.