I heard a fable one time about Jesus(substitute your favorite deity here) healing a leper clony and the first 5 or 6 said thanks you whole-heartedly and going on to rejoin society, but the next one staying to help clean up. And the moral was that Thankfulness goes backwards and Gratitude goes foward.
Whomever helped you was saying thanks for the last time somebody here helped them. Saying thanks is wonderful and one always should, but being of service the next time around is the real thanks.

Rich