I think what they are going for is you know all your secrets and insecurities. You might know what you look like before make up, or as you decompress from a hard day of work. You might wear baggy shirt to cover a small belly. You might wear flowing dresses because you don’t like your ass.
You compare that to people who wear yoga pants because they are proud of their ass. Or people who spent 45 minutes doing their hair and makeup that morning. You might see a guy with his shirt off because he spent hours in the gym working on his abs.
You know how you act/look your worst at home alone. You compare to how others look when they are out in public and dressed to impress.