הַמַּֽאֲכִ֨לְךָ֥ מָן֙ בַּמִּדְבָּ֔ר אֲשֶׁ֥ר לֹא־יָדְע֖וּן אֲבֹתֶ֑יךָלְמַ֣עַן עַנֹּֽתְךָ֗ וּלְמַ֙עַן֙ נַסֹּתֶ֔ךָלְהֵיטִֽבְךָ֖ בְּאַחֲרִיתֶֽךָ׃ 

  Manna From Heaven The One Who feeds you manna in the desert…in order to test you. (Devarim 8:16)  

Rabbeynu Bachya , ” All the tedium the people experienced during their trek in the desert was designed to subject them to a test to get them used to deal with such phenomena and to strengthen their faith when they would emerge from these tests each time. Faith in the Lord had to be instilled in them until it became their second nature (actually “first” nature). David asked for G’d’s assistance in training him to do His will until it would become
his nature to do so, until it required little effort. We find
the same wish expressed in Deut. 14,23 where the commandments of tithing and making pilgrimages to Jerusalem annually are used as prime examples of getting the Jewish people to “learn” to revere the Lord our G’d. The reason why the Torah describes a people being fed manna from heaven as suffering, enduring an “affliction” in doing so is to teach that when someone does not have a food supply for a number of days ahead he is considered as enduring an “affliction.” The fact that the supply of manna was only sufficient for one day at a time and the people had to depend on G’d’s goodwill on a daily basis was an ענוי, a serious discomfort. Even
the eating of such a limited food supply makes one conscious that there is nothing left when one has concluded one’s meal, a fact which lessens’ one’s enjoyment.