שבת: מנוחה מן הטורח והעמל

...It appears to me that the meaning of the midrash [interpreting the phrase “Shabbaton”] is that we are commanded on Yom Tov to rest from those activities that technically do not qualify as melacha, we should not be disturbed all day to measure our grain, to weigh our fruit and possessions, to fill our vessels with wine, to move our wares, and even building stones, from house to house and place to place, and if located in a walled city, load up our donkeys, and even wine, grapes, figs and all packages could indeed be delivered on Yom Tov; and the marketplace would be filled with ongoing commerce, and the shops would be open and money changers tables strewn with coins, and the workers would arise for their duties and establish their daily wages, like the rest of the week, and so on. These and similar activities, whether on Yom Tov or even Shabbat itself, all these activities do not technically constitute melacha. Therefore, the Torah commands us “Shabbaton”’ -- that these should be days of rest and cessation of work, and not days of labor and toil. And this is a good and beautiful interpretation.

There are activities that are forbidden on the Sabbath despite the fact that they do not resemble the [forbidden] labors, nor will they lead to [the performance of] the [forbidden] labors.
Why then are [these activities] forbidden? Because it is written [Isaiah 58:13], "If you restrain your feet, because of the Sabbath, and [refrain] from pursuing your desires on My holy day..." and it is written [ibid.], " And you shall honor it [by refraining] from following your [ordinary] ways, attending to your wants, and speaking about [mundane] matters."
Therefore, it is forbidden for a person to go and tend to his [mundane] concerns on the Sabbath, or even to speak about them - e.g., to discuss with a partner which merchandise should be sold on the morrow or which should be bought, how this building should be constructed, or which merchandise should be taken to a particular place. Speaking about all matters of this like is included in the prohibition [against] "...speaking about [mundane] matters."
It is speaking that is forbidden. Thinking [about such matters] is permitted.

1. When one reaches the words “to You, we give thanks,” in [the prayer] Nishmas, he should not bow as one does in the blessing Modim, for one should bow only in those places where our Sages instructed that we do so. RAMA: Our custom is that on Shabbat we come a bit later to the synagogue than we usually do on the weekdays, because the tamid sacrifice of the weekdays was said in the morning and on Shabbos we say "and on the Sabbath day" later. (Mordechai). And it is customary to increase the hymns of praise recited on Shabbos, every place according to its custom. In any case, if one does not say them we do not go back except if one did not say 'לאל אשר שבת'; for this one does go back and say it. It is befitting to prolong the hymns of praise recited on Shabbos and recite them with a pleasant melody as an expression of honor for the day. One should not admonish a sheliach tzibbur who prolongs their recitation even though the intent of the one delivering the admonishment is to prevent the neglect of Torah study. (Or Zaruah). In all cases, on Shabbat and Yom Tov we do not prolong their recitation too much, so we may eat prior to the sixth hour, as above in Siman 288.

On Shabbos, One Should Complete [the Quota] of 100 Blessings [by Reciting Blessings] on Fruits, 2 Seifim: 1. One must amply partake of fruits and sweets, and enjoy various fragrances if he possesses them, in order to reach the sum of 100 blessings. RAMA: If one is accustomed to sleeping during the afternoon during the week, he should not neglect [this practice] on Shabbos, because it is pleasurable for him. (Tur)