It's the hold the flesh has in us. We have no obligation to allow it any hold and even less to let it grow and fester there.
The Word instructs us to repent from double-mindedness, it is more than a general condition of being less than fully sanctified :
James 4:7 Therefore submit to God. Resist the devil and he will flee from you.
8 Draw near to God and He will draw near to you. Cleanse your hands, you sinners; and purify your hearts, you double-minded