If the soul is holy and the light of the Shechinah is all that is desired of existence, what then is the need of good deeds and physical actions?
Why is not the love of God sufficient?
But even for the most holy of saints, the man for whom the Divine presence is all, the one who is constantly consumed by love for God to the extent that he is unable to sleep at night, so agonized is he by the fear of losing conscious contact with the Beloved–even for such a one, the separation remains a hideous fact.
The "I" is still there, and there is no unification.
For the ultimate desire of the Tzadik is to be made null and void in the Divine and not to keep loving and yearning for Him, even in the paradise beyond the Garden of Eden, where the love of God reaches unimaginable heights of bliss.
The point is that the very existence of a separate self is an obstacle, for it is written (Deuteronomy 5:5) that "I" stood between the Lord and you.
It is not a matter of being on a higher or on a lower level.
As long as man is man, there is a barrier.
The very greatest love and fear of God are themselves only expressions of this abysmal gap between the human and the Divine.
It is the same fact as that which categorically states: "For no man shall see me and live" (Exodus 33:20).
If I am I, I cannot be He.
And all the experiences of the self, no matter how sublime, serve only to emphasize this truth.
On the other hand, the mitzvot are holy in themselves; they are not dependent on man.
Because the mitzvot are the will of God, it is possible by performing them to realize a Divine union that effects the desired nullification of self.
To be sure, it may be said that the whole world is an expression of His will.
But the world is by definition "something else".
It is that which is other than God.
It veils divinity.
For Creation was an act of contraction and concealment of the Divine face.
Whereas the mitzvot are a revelation of the Divine Will.
–Rabbi Adin Steinsaltz
From The Long Shorter Way by Rabbi Adin Steinsaltz