These ascents and descents create differences between the weekdays and Shabbat and all the other significant days and times, as well as between the nights and the days of the actual holidays themselves. Shabbat and the holidays are all times of ascent, and then afterwards the cycle swings around into a descent. The different ascents and descents either enhance or lessen the status of the creations (and thus the descent on weekdays represents not a flaw as such but rather a lessening in status.)
…in order to govern the worlds with the necessary measure of increase and decrease as required in any given circumstances. The Supreme Thought has already calculated which ascent is necessary and which ascent is unnecessary at every juncture, instituting the different times accordingly. Everything is arranged to bring the world to perfect government through all the different changes in the times.