We each have a tabernacle within our heart. A cloud of glory is over the tabernacle by day and a pillar of fire by night.
Both the cloud of glory and the pillar of fire symbolize states of consciousness, one in a setting of light (day) and the other in a setting of darkness (night).
The cloud of the "Glory of God" is the consciousness that all that God created in the world is "for His Glory," meaning that every aspect of created reality is ultimately intended to reflect and reveal the hitherto concealed Presence of the Creator. This is the consciousness of day, which according to the Chasidic adage is phrased, "all is God."
The pillar of fire illuminates darkness, i.e., reveals the essence of darkness (the essential meaning of seeing nothing in the dark), that all of created reality is dark, virtually non-existent, for only God truly exists. "God is all."
Chasidim conclude that you must have both, night and day, "God is all, all is God." This is the continual "run and return," the pulse and life-force of the essence of the Divine soul.