Psalm 107:21-22 says, "Oh that men would praise the Lord for his goodness, and for his wonderful works to the children of men! And let them sacrifice the sacrifices of thanksgiving, and declare his works with rejoicing."
Sometimes, the holidays can be a really tough time, especially if you know that people are having a great time, but you are miserable.
I remember when I was in the Air Force and I was in training. It was Thanksgiving Day, and I was in a simulation of a P.O.W. camp. That's where they treat you like you're a prisoner of war, so they can teach you how to act and possibly, what to expect. I was in a box, about the size of a refrigerator. I wasn't allowed to touch the side or sit down...all day. My thoughts drifted toward home, thinking about how everyone would be eating turkey and celebrating with family and friends.
It would have been really easy to have a pity party, but that wouldn't have helped. That was the perfect time to be thankful for all of the great times that I had experienced with my family, and to focus on the future times that we would have together.
It's easy to be grateful when everything is going great. It's when you're having a tough day, that you need to thank God and remember how good He is. Believe that things are getting better and better in your life!
Being thankful is really a declaration to the devil. You're letting him know that life is great now and will always be great to you!