He thinks about it too much and not enough. He's never ready for the shock of lust-need-pride-mine that slams into his body like a prizefighter whenever Charles arches his back and screams. Those breathless words on Charles's pretty red lips... "More. I can take it... Please, Logan, please, more..."
"Did I tell you you could beg?"
He should make it stop. He could make it stop. Charles said - all Logan's gotta do is say he doesn't want this anymore, and it'll stop...
Except, then it will all stop. This whole, crazy thing with Charles... It'll all be over. And no part of Logan wants that; especially not the part that only ever comes to life in the kid's cold, metal room. The part that didn't exist before Logan met Charles. That swells - that wants to growl and bite, like an animal - whenever Charles moans in pleasure or pain. The part with claws, and an appetite that scares Logan; a seemingly invulnerable desire to chase Charles's pain around his playroom and rip through it with the edge of their shared pleasures.
Logan wants to end Charles's hurting. The deep-down scar tissue that moves Charles to beg for Logan to hurt him in ways that can heal, can take his mind off of the wounds that can't.
But Logan doesn't want to "stop."
He's pretty sure that means that they're both fucked now, in ways that Logan can't pretend to know what to do with.