The only piece of paper I carry onstage is the set list. Everything else is memorised, and if I do forget a word or even a whole line, I carry on, not that I'm clever or anything, and laugh about it later. I'm only human, not a machine.
I don't like to see singers with sheets of paper - you may as well be reading your shopping list - it often makes for emotionless, robotic singing, sorry, but it's down to laziness. My brother, singing for 40+ years, always had bits of paper because he "just couldn't remember the words." Well, he's had a cataract operation, doesn't see so well, and is managing to remember the words just fine now!! Because he HAS to.

I rarely forget words because, I rehearse my songs over and over again.