Sleep would be wonderful, but if he was honest, even consciously he was afraid that that... thing might come and take him while he was unconscious. It was still too real a fear for him to be able to actively try to sleep, even if he could close his eyes for any length of time without a more subconscious terror taking hold of him and forcing them open.

The brightness of the sunlight outside hurts his eyes a bit, but it's a reassuring sight nonetheless, so he likes to focus on it.

"If you could make me forget that creature, that would probably help."

It's clear he doesn't actually expect Obi-Wan to be able to do something like that.