Psalm 50 says, "Make thankfulness your sacrifice to God, and keep the vows you made to the Most High. Because giving thanks is a sacrifice that truly honors me."
In being thankful, I acknowledge my dependence on Him and give respect to who He is and His greatness of a God. I find it worth noting that God counts sincere thankfulness as a sacrifice. Sacrifice often involves the offering of my skills and efforts whereas thankfulness takes nothing from me, or doesn't it?
Thankfulness must run deeper than just saying thanks then. Giving true thanks must TAKE AWAY all my expectations and to fully yield and have joyful appreciation of all that He has in store for me because I know He is great and He will never give anything less than what is best.