Another option other than the password managers everyone is talking about is those password notebooks, i mostly use one since try as you might; ya can't remotely hack a book.
Atleast use a Caesar's cypher to stop casual snoopers. Storing passwords in plaintext is bad, no matter the location or medium in which its stored.
Get a password manager.
Also, when you guess it correctly, a weird human shoves a camera in your face?
I use a password manager, which means if I ever lose access or forget my master password, there's zero changes in going to successfully guess my password to anything else, though.
Get a password manager.