Giles never struck me as an intellectual, and baseball is ultimately a cerebral game. Adrenaline carry carry you physically sometimes, but emotions have to be under control, especially as a pitcher. I think he often struggled with that part of his game.
ETA: to clarify, you can pitch with “fire” and determination, but you can’t let emotion dictate which pitch you throw next. If you’re getting squeezed, you have to adjust, you can’t get into a dick measuring contest with the ump. If a guy hits a fastball, you can’t be afraid to throw it the next time up. A fastball may not be the best pitch, but you can’t be sacred to throw it if it is. You can’t keep throwing a guy fastballs because you’re pissed off and want to announce your presence with authority. Ultimately you have to pitch with a purpose. Giles seemed to get lost in that sometimes.