What makes a job a mission?

I have been contemplating this question now for about three weeks and have several ideas.  First, I don't think "a job" is necessarily a bad idea.  There is a fundamental need we all have that is to provide for our families.  It is therapeutic to work and our jobs are healthy ways to grow and provide for others.   When our job becomes our mission, however, I believe we work for a higher calling or for a bigger reason than just to provide for our families. This should make our days more fulfilling.   Here are a few thoughts on what makes a job a mission:
1.  The person working determines whether or not the job is a mission.  I suppose if we interviewed missionaries some would say they have witnessed "missionaries" treat their mission like a job.   In other words, just calling something a "mission" will not necessarily bring about the deeper sense of engagement or fullfillment one might expect as they pursue the goal of helping others.
2.  The motivation behind the work.  If our work is focused more on ourselves, our work may become mundane and we may become selfish with our behavior.  When our work is focused on helping others, we may work harder to go above and beyond to assure satisfaction and that goals are met.
3.  Whether or not someone is paid...actually, even "missionaries" get paid (usually) to do their "missions."  I think working for money can create a tendency toward selfish behavior that we must overcome to maintain a more pure selfless frame of mind.