One of the most important discoveries in my life was the importance of gratitude. Not as a response to a set of favorable circumstances, but a constant, proactive approach towards reality. A choice. If happiness is wanting what you have, then the key to that happiness is gratefulness.
Lately, I had yet another discussion on organizational change and mindsets. Obviously, you cannot force another person to change his or her mindset. You can, however, look for ways to help that person feel grateful for a particular job, for being part of one special team.