Self-interest or fear?

Motivation is the reasons for people to get involved in some specific activities. When people are motivated, they can work better and achieve higher results. The incentives to work of different people are also not the same, and even for one person, the drive for their work changes during times.
People go to work for the job they chose as they like it, and they feel happy doing it. However, others may do things for the benefits it brings back to them, for example, workers go to work everyday just for living, for money, not because their love for it. Moreover, even with your dream job, after a long time working you may get tired and bored with it, at that time, you go to work just because you have to do it or you will lose your monthly salary, lose your high position in the company and even lose your house.
Self-interest is not the only incentive for people to work, fear is also a very good force that motivate people; for example, students come to class and do homework everyday not only because they love studying but also because the scare of failing the class or getting bad grades which is not good for their future career.
Besides, there are also some feelings other than self-interests or fears like angry, respect or sympathy that lead people to work. When a person gets angry, they are full of energy and can use that energy to fight, to do housework, or to shout at others. Another example is the volunteers, they join the work because they like it, they want to do it rather than they benefit from it.
There are many drives push people to work, some are positive like the love and desire to work; others are negative like their self-interest, fear or angriness. However, no matter what the reasons are, if a person can lead it to good and meaningful work, it is fine.