Googling it I found out it’s from Tony Morrison’s The Bluest Eye. It’s a difficult paragraph to understand. I would have to read quite a bit of the preceding text to understand exactly what is being said. “sabotaging it” could refer to either “despising glance” or something in the preceding text. It could mean something like “It’s difficult to describe a viewpoint while you’re trying to show that it’s not a valid viewpoint”. “agency” can mean something like “action producing a particular effect”: ‘canals carved by the agency of running water’ “the agency I discovered in my first experience of beauty” could mean something like “the effect my first experience of beauty had on me”