This is a great article explaining the value of a 'grateful heart' and the lack of grateful heart as a sign of unhealthy narcissism. I was originally searching for a copy of McWilliams and Lependorf's excellent article, The Denial of Remorse and Gratitude (which appears to no longer be 'free' on the web), and fortunately stumbled upon this pdf document. It's definitely worth a read!
Guess that means I'm really, really grateful to have found it.

And I'm extra grateful it's still 'free'.

Hugs,
CZ
“...Based on clinical observations, McWilliams and Lependorf noted that narcissistic people are incapable of experiencing and expressing sincere gratitude. A core issue for narcissistic people is their slavish adherence to self-sufficiency. Expressions of gratitude are acknowledgments that one is dependent on other people for one’s well-being, and therefore not self-sufficient. Given this reality, such individuals find expressions of gratitude to be highly unpleasant. Furthermore, because narcissistic individuals possess a distorted sense of their own superiority, they might be reluctant to express gratitude in response to benefactors whose generosity or kindness they summarily dismiss as little more than an attempt to curry favor.
“…found that in the context of a laboratory-based interdependence game, narcissism was inversely related to the extent to which participants experiences liking and gratitude for their partners.”
Click
HERE to retrieve 13-page document