To get to the level of holiness, a certain struggle is necessary, a virtual war, like between nations in the womb of Rebecca when she was carrying the twins, Esau and Jacob.
The twins are born with us, they accompany us throughout life, and they continue the struggle.
As it has been written, were it not for God’s help, we would probably not be able to overcome the foe.
Every day the impulses of the lower nature come forth to draw man down to death, and he has to rely on Divine support to maintain himself.
In this persistent war between fairly even sides, only man’s constant choosing the good saves him.”
–Rabbi Adin Steinsaltz
From In the Beginning, “Overcoming the Obstacles to Lower Unity”, pp. 220-221