The Sabbath is essentially the day of rest, of cessation from all labor and creative effort.
And this holds true for the spiritual effort of working on oneself as well as for the physical effort of working on the world.
The week is characterized by busyness or activity, while the Sabbath is grounded on stillness, on the nullification of oneself in the downpour of holiness.
And this self-repudiation is expressed by a renunciation of all work, whether it be in the physical sense, as being busy in the world, or in the spiritual sense, as engaging in efforts to correct one's soul.
In fact, the very power to receive the spiritual essence of the Sabbath comes from one's readiness and ability to surrender, to give up one's human and worldly state for the sake of the Supreme Holiness, through which all the worlds are raised to a higher level.
–Rabbi Adin Steinsaltz
From The Thirteen Petalled Rose by Rabbi Adin Steinsaltz