There are better routes than "Correct Horse Battery Staple".
Think about how memory champions memorize arbitrary data: yes, it's visual, but it's not random words stuck together like "Correct horse battery staple", it's a meaningful scene, something you could describe with a sentence. Now, of course, that's too bulky to make a password. But you can deal with that easily - the easiest way is just take the first letter of each word, an abbreviation / acronym password. For the first sentence in my post, depending on how you apply the rules you may get something like tabrtchbs or Tabrt"CHBS" or the like.
Now, obviously on an attacker can reduce the search space with statistical analysis of sentences, but overall sentences yield an extremely random password - moreso than "Correct Horse Battery Staple", it's much shorter, and it's easier to memorize. And if the security of such a standard approach isn't good enough, you can apply your own extra rules, such letter substitutions, arbitrarily inserted characters, change the order of the word or what letter you pick from each word, etc.