(condensed from Ein Ayah, Berachot 5:107)

Gemara: Rabbi Chanina said: All is in Heaven’s Hands except for the fear of Heaven.

Ein Ayah: The true shleimut (completeness) is to resemble Hashem to the extent humanly possible. A prerequisite of shleimut is total freedom, which is a sign of full ability. If there is something that is forcing someone, then he is not free and capable.

The highest level a person can reach is to possess fear of Hashem, which enables one to adorn himself with the full realization of Hashem’s Honor. Therefore, it must be connected to the high level of full free choice. Therefore, fear of Hashem was left to complete free will and is not dictated from Above, so that man can reach as close to Divine attributes as is humanly possible.