Just write it down. Eventually, you'll memorize it. It will be faster if you challenge yourself each time: see how many characters you can type before having to look.

It's important to keep in mind threat models. The biggest threat is that someone attacks one website you use and uses that password to take control of your account on another website. The password manager solves this problem. (It also give you strong passwords, which is overkill.) People physically close to you that might steal the piece of paper with the password aren't much of a threat and even if they were, they probably wouldn't figure out the meaning of it. But you can destroy it after memorization.