A "good password" depends on what you want it to be good for. If you want it to be good in terms of "I will never
forget this password, even when I've not logged into this system for four years" then a password you'll always remember is
just the ticket.
I have a few standard passwords that I re-use from machine to machine. If I find myself in front of a system I've not used for a long time and wonder what my password was, I invariably try the two or three standard passwords I reserve for these occasions.
Of course, password aging defeats this approach. Which is another point entirely. Data is only as secure as the system on which it resides. The best password in the world won't protect your data if the system on which it is stored is a UNIX machine with no root password set, to use an extreme example.
Did you know that the most common password that people choose is "password"? The problem these days is that every website under the sun wants you to log in, and requires a password. I don't know about you, but remembering twenty password mnemonics is beyond my limit.