The Talmud states (Berachot 58a) - A gracious guest says "The host toiled for me, brought so much meat, wine and loaves before me. All he toiled was only for me." An ungracious guest says "What toil? I ate one slice bread, one piece meat and one glass wine... all his toil was for his wife and children."
The two guests may actually be factually correct in either case. The good and bad here are that a gracious person has developed an inner need to express appreciation whenever he/she feels any good.
The Gaon says that the host in this Talmudic passage may also be G-d. As it says in Pirkei Avos (Ethics of the Fathers), a bad person says 'What's mine is mine, what's yours in mine,' while a pious person says 'What's mine is yours, what's yours is yours.' If this saying is applied to G-d, 'what's mine is mine,' becomes an ungrateful statement to G-d that all G-d gives us is for His pleasure anyway, and ultimately G-d will get more pleasure from giving to us. On the other hand, saying to G-d 'what's mine is Yours', while still recognizing that all G-d created is for our good, it is a statement of appreciation, that it did not come from deserving it.
In the Haggadah, the song 'Dayeinu' is juxtaposed between the recounting of the events of leaving Egypt and the songs of praise to G-d. It says, that all these things that happened we did not deserve. It is a type of song that a person who has a sense of appreciation sings immediately upon being bestowed kindness.
- adapted from Kos Eliyahu by Rabbi Eliyahu Safran