Are you thanking God for all He has provided; or looking around with discontent?
And the mixt multitude that was among them fell a lusting: and the children of Israel also wept again, and said, Who shall give us flesh to eat? We remember the fish, which we did eat in Egypt freely; the cucumbers, and the melons, and the leeks, and the onions, and the garlick: But now our soul is dried away: there is nothing at all, beside this manna, before our eyes. (Numbers 11:4-6 KJV)
I know you have done the same thing. You are hungry and begin combing through the cupboards in your kitchen to find that perfect snack. The longer you look the less likely you are to find something that seems satisfying to the physical hunger which seems to rage within you. You have good food to eat but not what you desire to eat in this moment of hunger.
Mankind suffers from both physical and spiritual hunger. Yes, we often search, sometimes to no avail, to fill that hunger pang our heart, rather than our stomach desires. Sometimes we look back into a time in our history when life seemed more fulfilling and yearn for that which seems familiar and comforting. Or we look upon those around us who seem to have everything while we are in need of many things as we change our focus from thanking God to discontentment with the provisions of God as we look around instead of focusing upon Him.
Those who are led by the spirit of the god cannot find lasting satisfaction with the things of this world. They see many empty cupboards in their quest to fulfill the hunger that churns within them; both of a spiritual and physical nature. Those who are children of God learn to be spiritually satisfied with all that God provides understanding that He always has our best interests at heart.
How insulting it must be to God, Provider of all, to hear man whining and complaining about what they do not have rather than being thankful for what He has mercifully provided to them; not because they deserve anything, but simply because He loves them unconditionally.