God must “reign” in the “central will or personality”

“… I think we all of us know, as a matter of practical experience, that there is something within us, behind our emotions and behind our wishes, an independent self, that, after all, decides everything and controls everything. … and if God is to take possession of us, it must be into this central will or personality that he enters. If, then, He is reigning there by the power of His Spirit, all the rest of our nature must come under His sway… (Hannah Whitall Smith, The Christian’s Secret of a Happy Life, “Difficulties Concerning the Will”)