For me, gratitude doesn't feel like a behavior that I choose to engage in in order to reap psychological and interpersonal benefits. Rather, I find I have this profound gratitude for the fact of my stupendously improbable existence, and I'm productive in order to express this gratitude.

This nicely doubles as an ethical standard. When faced with choices, I can ask myself "which option best expresses my gratitude for my existence?" and that works for me.