thanksgiving and bereshit

Tonight in Mishmar, we were learning about whether Jews are obligated to give thanks or not, in honor of the approaching holiday of Thanksgiving. We saw that there are many sources which say we are, and all the various places that it says so. This got me thinking about everything we have learned this year in Bereshot and the history of the Jews in general. We are known the complain a lot. In the desert, we complained over water, food, meat, etc. We were never happy with our lot even when we had just been through amazing miracles. This made me wonder if the same is true in Bereshit. People have just been created, and are put in a beautiful place where everything is given to them, yet do they ever utter a word of thanks? No. Instead, they take advantage of this and get kicked out of the garden. Later on, when Cain sins, G-d has mercy on him, but is Cain grateful? No. Next time something good happens in your life, take a moment to be grateful and realize what a good life you have and appreciate what G-d has given you