correct battery horse staple, but longer and sensible but still unique, and optionally without space.
Make up a sentence that makes sense to you, and remove all the spaces, use all lowercase and no special characters.
Forgettable: 5uP3r53kr17P455w00r[)!!11One
Memorable: ilikestartrekandhamandbeans
I used to have full-disk encryption on one of my machines using a password of the forgettable kind. But then the machine had an uptime of months until a power outage, and I realized that while I was fairly sure of the sentence I had no possibility of remembering all of the uppercase and lowercase and symbol and number substitutions. I lost quite a bit of data that day.
After that I began using a sentence that makes sense to me but which is not from a book or anything like that for the FDE on my desktop and external hard drives, and I use the pass phrase frequently. Simplicity and repetition is the key to remember your master password.
As for websites I use a password manager, and I sometimes generate passwords with my own diceware software https://github.com/ctsrc/Pgen but most often I am on my phone or on my laptop and then I use the password generator of the password manager that comes with those Apple devices.
I haven’t lost any more data since switching to managing my data encryption and my passwords this way.