Thankfulness is the beginning of gratitude. Gratitude is the completion of thankfulness. Thankfulness may consist merely of words. Gratitude is shown in acts.

Saying thank you and being grateful are not the same distance along the same road. Words can be sincere and still cost nothing, and they can be finished the moment they are spoken. Gratitude keeps going. It shows up as a returned favour, a call you make, time you give back, care you take with something someone handed you.

Think of one person you have thanked recently and ask what the thanks would look like as an action. Then do that instead of saying it again. The small repayments land harder than the phrase, and they are usually remembered longer.