Shows appreciation for good fortune and life in general.
High scorers both (1) notice reasons to be thankful and (2) express those feelings. Gratefulness can apply to life in general and specific acts.
General gratitude for life results from awareness and appreciation of things that can easily go unnoticed. Even in hard times, grateful people can appreciate lessons learned. And in good times, they don't take good fortune for granted.
Gratitude for specific acts relates more to other people: noticing how other people have contributed to your life and taking the time to express that appreciation.