Oh, it is.
It's decades more secure than some random 8 digit that you can hardly remember.
Passphrase > Password
It might be better than average secure but not much more. Something I read from one of the links here was to include characters not in the standard alphabet. Your method would crack a lot sooner that something like @tPP89*&77br/?xX for example.
Despite reading 'Moonwalking with Einstein' I gave-up trying to remember my passwords. You should generally speaking only need to remember one or two.