The question was asked: Why can't one reach a state of union with the Shechinah by means of intense devotion?
why is it not possible through love, profound awe, ecstasy, or any other subjective manifestation of the soul?
And the answer was that it does not depend on any personal feelings or thoughts, but on certain actions or situations in which the person becomes a vessel for the Shechinah.
The difficulty for most men is that one's very humanity seems to make it impossible to be an abiding place for the Shechinah.
Because, although the outward sign of such an indwelling is the Divine light, the inner consequences are that the one in whom the Shechinah abides ceases to be an individual self.
To be sure, all creatures are instruments of the Divine, but one cannot say that the Shechinah dwells in them.
For that in which the Shechinah abides becomes null and void of any being of its own.
And that which retains anything of its own being cannot manifest the Divine light.
From this, it seems that this deeply desired unity with God cannot be reached so easily, either by passionate devotion or by certain duly performed steps or actions.
Not that man should ever cease to progress and strive for an ever higher degree of love and awe of God.
And there are always higher and ever higher levels of being.
Even Tzadikim are said to be restless men.
As one of them put it: That level, which yesterday was the Heaven above, has to be made into the ground on which one walks today.
–Rabbi Adin Steinsaltz
From “Problems of Receiving the Shechinah” in The Long Shorter Way by Rabbi Adin Steinsaltz