the.com/blind spot

means An area or aspect you consistently fail to notice or judge clearly, often about yourself.

from Literal before it was figurative: the term comes from the anatomy of the eye, naming the small patch on the retina where the optic nerve exits and no light-detecting cells exist — so the brain simply paints in a guess to cover the gap. By the 19th century, writers borrowed the phrase for the mind's version of the same trick: a gap in perception you don't notice precisely because something else quietly fills it in.