Fallen nature refers to a mentality that is derailed from the original track of the Principle that God originally intended. Then, how can human beings return to the original track of the Principle, removing the fallen nature?
The reason why God loves us without any reasons or conditions is simply because we are His children.
Human beings who are derailed from the original track should return to the original position as God's children. However, to do this is impossible without establishing a proper condition.
Then, what is that condition?
When human beings, created as the children of God, fell, by being derailed from the original track, they came to serve another master, resulting in their attending two masters.
However, they should clearly realize that God is the true master. That is, only when they return to God after leaving their position of dealing with two masters can they be fully restored.
Sun Myung Moon