There are very few passwords you should have to memorize. The only passwords I have memorized are my personal Apple ID, my Bronco NetID, my personal Gmail account, my Dashlane master password, and the password to a shared work KeePass file. For those passwords you must memorize:
Use four or more random words or a phrase.
Take inspiration from poetry, books, or movies:
Every other password I use is stored in a password manager. I use Dashlane for all of my personal accounts and I share a KeePass file with two members of my department for shared work accounts.
Using a password manager allows you to have incredibly strong passwords that are:
Create random, unique passwords by using a random password generator:
I use the following settings when creating random passwords: