I've just finished reading "Flow" by Mihaly Csikszentmihalyi, which deals with the subject of how to achieve happiness and enjoyment from work.
The fundamental thesis is that people most enjoy activities in which the goals are clear, the are opportunities for action towards those goals and feedback is immediate. Mihaly delves at length into the concept of an "autotelic personality" - that is, a person who is able to:
1. set their own goals, balancing both long term high level goals with shorter term more immediate goals, and
2. create opportunities for action (rather than feeling like a passive observer or even a victim).
Mihaly also goes into great depth about the difference between people who rely on external goals, such as greater wealth, more fame, etc., and those who are more focused on more intrinsic goals such as developing their personal skills and cognitive abilities. Unsurprisingly, he suggests that latter are more resilient to environmental difficulties, and therefore more likely to sustain a sense of well-being regardless of what is happening around them.
When all of these conditions are present, it is said that you will be in a state of "flow". Your concentration will become focused, and your daily stresses will recede from consciousness. This, suggests Mihaly, is the key to sustained happiness,
It's a fascinating and well researched book, with numerous anecdotes to demonstrate the theory. I can highly recommend it to almost everyone.