If his body weren't used to it, even with his high Spirit, he would subconsciously reject this state, limiting his duration inside. If he forcefully tried extending it without his body getting used to the sensation, it could cause irreversible damage to his mental state and he might really fall into darkness without getting back.
Webnovel 
wasn’t*
If his body weren't used to it, even with his high Spirit, he would subconsciously reject this state, limiting his duration inside. If he forcefully tried extending it without his body getting used to the sensation, it could cause irreversible damage to his mental state and he might really fall into darkness without getting back.
Arcane Academy: The Divine Extraction Legacy
Fantasy · xlntz