Just as the food enjoyed on Shabbat has to be cooked beforehand, it does not just appear out of the sky, Shabbat is the time for enjoying what was prepared during the week.
The awakening of delight is the result of the performance of mitzvot during the previous days.
The Shabbat is not a free gift.
The conclusion to be drawn from this is that whatever a person is during the week, he is the same on Shabbat.
If a man behaves like a dog during the six days, he remains something of a dog on the seventh, except that he is now a Shabbat dog…
–Rabbi Adin Steinsaltz
From The Candle of God, p. 40, by Rabbi Adin Steinsaltz