True thankfulness comes from the heart.
If you want to be truly thankful, here is what you should do. After praying maghrib, sit down and think. Think of things to thank Allah for. You should be able to easily come up with at least 10 things.
Once you feel thankful, perform two Sunnah rak'ats in a state of thankfulness. Now Allah sees that you are a truly thankful servant.
Photo: Reused from Changing Oneself.