My understanding is that God and the Devil are often present in our actions. When we work with great energy it's because our best motive and our worst motive--or, to put it another way, God and the Devil--are equally engaged in the outcome and so, for a period, working within us. There can be collaboration between opposites, as well as war. This collaboration can consist of certain agreements--"The rules of war will be..." And of course, the rules can be broken. The Devil can betray God. Once in a while, God also breaks the rules--with a miracle. But my argument is that when we act with great energy, it is because God and the Devil have the same interest in the outcome. (Their differences will be settled later.) Whereas when we work with little energy, it's because They are not only at odds but are countermanding each other's impact upon us.
I would expect God creates new spiritual lives. God may say, "I've been reconsidering the terrible propensities of the Devil. Let us see if we can conceive of a soul who will be able to war with the Devil a little more effectively, a new soul who will have many of the qualities of the Devil but can transmute them, transform them, elevate our sense of spirit even in the dirtiest, ugliest, foulest places. God may have decided that an iota of goodness in an evil soul can be immensely important."