What if you add your own personal coding to the obvious phrase?
Lets say, replace all the letters A with B.
For example "cbptbining finbncial conservbtism mbyonnbise" instead of "captaining financial conservatism mayonnaise"
Will it more difficult to get the key?
I think the point of this entire thread can be summed up as follows:
Give up and use a secure random number generator based on a qualified true random number source of entropy unless you want to lose your Bitcoins.