The essence of life in the world, as formulated in Jewish writings, is exemplified by the terrible progress of the divine fire (Ezekiel I) to and fro, up and back-the constant rhythm of the breath and the heart’s blood.
This principle of fluctuation seems even to be at the root of man’s relation to Heaven and earth, evinced as the urge to extricate oneself from the bonds of matter and rise toward the Divine, and the equally urgent need to return to the world, with its problems, its substantiality, its life of sadness.
To remain in anyone condition of being, above or below, represents a cessation of effort, a dying, and therefore an evil.
At times the yearning for Heaven is great enough to make one leave behind the world and everything in it.
At other times the clutching at the earthly realities of action and the fulfillment of desire make one forget all else.
This is not only a matter of periods in one’s life; it is the very nature of life itself:
In both the ascent to God and the descent to matter there is holiness.
Never is anyone way wholly sufficient unto itself, and it is only when they exist together that they constitute a real passage between Heaven and earth.
–Rabbi Adin Steinsaltz