David directs his soul, "Return, my soul, to your rest, for Hashem has been kind to you (Psalm 116:7)."   After experiencing persecution and difficulty, David’s soul is feeling battered.   It is only normal to feel "soul fatigue" when one has encountered emotionally and spiritually wrenching situations.    This "soul fatigue" can be countered by clinging to Hashem.  Returning to G-D results in a spiritual recharge.   We have a long history with Hashem, having personally experienced His concern and kindnesses.  On Shabbat, we return to Hashem, shedding the demands of the workweek.   The serenity and spirituality of Shabbat revitalizes us, and carries us till the next Shabbat.