The Dark Tower. Book 4. Wizard and Glass

He’s using every ounce of his will to keep from going back, anyway, Cuthbert thought. He found the realization comforting—sometimes Roland scared him. There was something in him that went beyond steel. Something like madness. If it was there, you were glad to have it on your side . . . but often enough you wished it wasn’t there at all. On anybody’s side.

Roland had no thought of retreating, or perhaps jigging to one side or the other. He had, in fact, no thoughts at all. The fever had descended over his mind and he burned with it like a torch inside a glass sleeve. Screaming through the reins caught in his teeth, he galloped toward Hash Renfrew and the three men behind him.

She worked against the feeling as best she could, holding onto her mind, refusing to let it turn into what it had been before and would be again if she let it—a brainless bird trapped in a barn, bashing into the walls and ignoring the open window through which it had entered.