The Midrash (Koheles Rabbah ) interprets this verse to mean that the manna was "a food of hunger". One of the reasons for this was because the manna could not be saved from day to day and one needed to trust and rely on it falling anew the next day. The manna was therefore called a food of affliction, because "One who has bread in their basket is not comparable to one who has no bread in their basket (Talmud, Yoma 74b)." The perceived lack of security left the skeptic anxious and uncomfortable even after filling himself on manna.
We find, however, that Moshe instituted the first blessing of Birchas Hamazon when Bnei Yisrael were granted the manna, in fulfillment of the commandment (Devarim ), "you will eat and be satisfiedand bless G-d" (Berachos 48b). How could the consumption of themanna be cause for a blessing to thank G-d for satisfaction, when in fact it was a "food of hunger" and affliction?
Unlike all other aspects of the physical reality, the manna was unique in that it was obviously being regenerated anew by Divine will each day, and it had no "life of its own". Conversely, in foods that have a shelf life or "basket life", the Divine energy that is recreating them at each moment is not evident; their continued existence seems inherently certain, and not dependent on any "outside" influence.
Consequently, the very "deficiency" which caused the manna to not satisfy the person who sought confidence and self-reliance, would make it the greatest source of satisfaction for the humble man of faith who values a constant and revealed relationship with G-d. Hedelights in being sustained by means in which G-d's influence is clear and revealed, and not from sources where G-d's active involvement is obscured. The manna's direct revelation of the Divine satisfies him more than the sense of security provided by material means, making the manna the food over which it can most fittingly be said, "you will eat and be satisfied" and therefore, "bless G-d."
—Toras Menachem, Sefer Hamaamarim Melukat vol. 4, p. 186