Most account passwords do not need memorizing: generate unique random values and save them in a password manager. Reserve a memorized passphrase for the manager itself or a device unlock. Build it from randomly chosen, unrelated words rather than a quote, a personal story, or a pattern someone could infer.
Length helps, but the selection method matters too. Four familiar words you chose to fit a theme can be more predictable than random words. Practice typing the passphrase, store a recovery method safely, and turn on additional authentication where supported. Do not submit a real passphrase to a web strength checker; test candidate patterns with disposable examples instead. NIST's password guidance explains the limits of simple entropy scores.
Akousa