My suggestion, choose a difficult to remember phrase with many misspellings, etc.  Repeat it to yourself daily.

As a second level of security, write this passphrase down and then split it with shamir's sharing secret into 5 pieces with a quorom of 3.  Hide them in different places.  If you ever forget your phrase, you only need to retrieve 3 of them to recreate your passphrase and use that to regenerate your private key.