The trick is using something you can easily remember but also not obvious. For example: take your favorite book, pick the first sentence of the first chapter and change vowels with numbers. There, super easy to remember password, but almost impossible to guess.

Instead, you can use anything: the second sentence of the book, the name of your favourite song (or songs if the song is just one word), the lyrics of that song...

Just something that is easily accessible in case you forget but nobody could ever guess