The solemnity of the Shabbat meals, and of Shabbat in general, should not be taken to imply heaviness or gloom, nor should the element of restriction be allowed to predominate.
On the contrary, festivity is of the essence.
Even one who is newly bereaved or has a fresh memory of some other personal catastrophe must stop mourning when Shabbat arrives.
The neshamah yeterah ("extra soul") each Jew is said to acquire on Shabbat is really an augmented ability to rejoice in tranquillity, to cease doing things as if all were already done, to accept life with a feeling of wholeness and contentment.
Not only is Shabbat a time to disengage oneself from workaday affairs—even reading, speaking, and thinking about them are forbidden—but when it comes to spiritual matters, too, vexation and anxious self-analysis should be avoided.
The holiness of the day must be sought in a spirit of oneg Shabbat ("the joy of the Sabbath"), of pleasure, relaxation, and ease.
–Rabbi Adin Steinsaltz
From "Shabbat" in Teshuvah by Rabbi Adin Steinsaltz