[He might be used to those feelings, but it also means he knows how hard they can be to deal with. So he's doing what he'd want someone to do for him when he's recalling them, and hugging Porthos tight, rubbing his back, murmuring softly that it's fine, that he loves him.]
[He only just so bites back the apologies he wants to tell him, because he knows it'd only upset him further. But he really, really didn't want you exposed to something like that.]