Here is a one-sentence formula for becoming a grateful person: Think, speak, and act like a grateful person does.

There is no mystery on how to become a person with the attribute of gratitude. Think gratefully. Speak gratefully. And act gratefully. When you consistently do these three things, you are consistently grateful. And even before you are consistent with this pattern, every little bit of thinking, speaking, and acting this way makes you more grateful than if you wouldn't have thought, spoken, or acted this way.