Life Hack #1 - How Can I Hide Something I Have Written?

I make mistakes when writing that I feel silly for doing. I also jot down notes and need to cross them out for privacy reasons. I don't want the person who reads it to be able to see it. I needed a life hack that worked better than just crossing out over and over or hunting for a black felt tip. This is what I found. Do you have any other tips for privacy?