I’ve often wondered for what reason God gave us Shabbat (emulation of God’s acts of Creation aside).
I tended to think that it was a compassionate response to the slavery that Israelites had recently (at that point) endured. In slavery, there are no regularly-scheduled “days off.” To those who had spent their lives working without stopping, God was now giving the gift of a day off every week!
But it occurred to me, too, that there is a more universal meaning.
“Work” itself was something that all humankind was compelled to do because of Adam and Havah’s error:
“Cursed is the ground because of you; through painful toil you will eat food from it all the days of your life.
Both thorns and thistles it shall bring forth for you, and you shall eat the herb of the field.
In the sweat of your face you shall eat bread till you return to the ground…” 
Although Adam and Havah were previously to tend Gan Eiden, it’s not meant to suggest any hard work; certainly not to feed themselves. Vegetables and fruit grew everywhere. All that was needed was to stretch out their hands and pick what they wanted, whenever they wanted it.
After their error, they were compelled to work hard every day of their entire lives to preserve life and health.
So, when God later says:
“Six days you shall labor and do all your work,
but the seventh day is a sabbath of your God; on it you shall not do any work…” 
God was modifying a condemnation that had otherwise been categorical and worldwide. It was a supreme act of Hesed — lovingkindness by God. It was an act of forgiveness, of pardon, that only God could give.
In Megillat Esther, for example, the King (Achashverosh) allows Haman to attack the Jews. When Esther entreats the Achashverosh, he can’t withdraw his edict because a (human) King couldn’t negate his own edict — but he could issue another allowing the Jews to defend themselves. God, too, having created a world in which actions have consequences, can’t (or wouldn’t) nullify those of Adam and Havah’s act. But God can modify those consequences — especially depending on subsequent factor and conditions.
“The Sages stated that the blessing of Shabbat was reflected in the double portion of manna that fell . One might be inclined to ask what kind of blessing this was, since, in fact, the amount of manna that the people received on Shabbat was the same as that of the rest of the week; it simply fell a day early. The answer is that on the seventh day they did not have to worry, because their Shabbat food had already been prepared on Friday. This can be compared to one who had to work hard every day. One day he managed to finish two days’ worth of work. The next day he felt a sense of great relief because he did not need to work, and he was free to think about things beyond his immediate needs…This is the blessing of Shabbat. We are commanded to stop working and stop worrying about money, and through this freedom and liberation we cling to God and His Torah…” 
If on the surface, we are told “don’t work,” the rabbis indicate that the deeper observance of Shabbat means to relax our life-concerns altogether, putting them entirely in God’s hands.
Not only are we “commanded…to stop worrying about money [etc.],” but we receive an additional soul, as it were:
“…on Shabbat Eve G‑d gives a person an ‘Additional Soul,’ and at the conclusion of Shabbat it is taken from him.” 
But that “additional soul” is nothing other than the deepest levels of what we actually are:
“…the Additional Soul is not something that comes from outside of a person, but is a revelation from the deepest part of a person’s essence.” 
The “additional soul” isn’t taken from us at the end of Shabbat. It can never be taken from us. It is us.
But it can be overshadowed; re-obscured again by the return of our attention to “food” — i.e. to mundane concerns and attachment to the results we desire.
Thus, the mitzvah of Shabbat is the beginning of a fundamentally spiritual redemption, foretelling a future that is “wholly a Shabbat:”
“The Blessed Holy One created seven aeons [millenia]…The seventh aeon is entirely Shabbat and rest in eternal life.” 
“‘…A psalm, a song for the Shabbat day …’ For a day which is wholly Shabbat, [a day] in which there is neither eating nor drinking nor trafficking [i.e. work or business], but [in which] the righteous sit with their crowns on their heads and are nourished by the splendor of the Shechinah, as it is said, ‘…they beheld God and didn’t eat or drink…’  — like the ministering angels.” 
In many ways, “work” has mainly to do with our efforts to feed ourselves — i.e. to keep ourselves alive. The disciplining of Adam and Havah is that they will have to work hard to feed themselves. In the Wandering, the Israelites are freed from the necessity of working to gather food on Shabbat by dint of the double portion of manna given on each Friday. The rabbis teach that in the future, food [i.e. effort or concern to preserve life] won’t be a consideration at all. Life will be effortlessly preserved — “nourished” — by the Divine Presence alone.
This similarly characterizes “Cosmic Consciousness” — the first level of spiritual enlightenment — as explained by Maharishi Mahesh Yogi:
“…This state of cosmic consciousness [note: Maharishi did not use upper-case letters] is one where the mind lives in eternal freedom, remaining unbound by whatever it experiences during all activities in the relative world. This freedom from the bondage of experience gives the mind a status of cosmic consciousness — a condition of eternal freedom in all the relative states of life — waking, dreaming and sleeping.” 
Some years ago, I read of a debate among the students at Yeshivah University (NY). The issue was whether setting a time to turn on a TV on Shabbat, in order to watch football games, was a “violation.” Those arguing in favor of it pointed out that they were not turning on the TV themselves (which would have been an inarguable violation).
But we can see that the rabbis understood observing Shabbat to mean not only what we don’t do, but to include where we place our attention: i.e. on God.
Shabbat was a gift of pardon and lovingkindness that we receive anew each week — until the time when it is the very nature of our lives.
 Bereishith/Gen. 3:17-19
 Shemoth/Ex. 20:9-10
 Bereishit Rabba 11:2
 Rabbi Eliezer Melamed
 Beitzah 16a and Ta’anit 27b, from
 Friedlander, Gerald, trans.; Pirke de Rabbi Eliezer, ch. 18; Sepher-Hermon Press, © 1965 (4th edition 1981); p. 141
 Tehillim/Ps. 92:1
 Shemoth/Ex. 24:11
 Goldin, Judah, trans.; Avot de Rabbi Natan/The Fathers According to Rabbi Nathan, ch.1; © 1955 by Yale University Press (Schocken Books edition 1955); p. 12
 Maharishi Mahesh Yogi; The Science of Being and Art of Living; SRM Publications, © 1963 (from 1966 edition); p.250