First, find out your own top strengths:
The best way to diagnose your own strengths is to take the full "VIA Signature Strengths" test at www.authentichappiness.org. You should go to that site and register yourself, so that you can take multiple personality tests and keep all your scores together. Note that the full Strengths test will take 20-30 minutes to complete. If you want a faster but less accurate way of diagnosing your strengths you can print out the "Signature Strengths Self Rating Scale."
Second, improve the fit between your strengths and your job
Knowing your strengths -- and weaknesses -- may give you insight into why some parts of your job are enjoyable while others fill you with dread. If you have the luxury of adjusting the scope of your job then of course you should focus on the tasks that draw on your strengths while delegating away the parts that don't -- even if you are perfectly competent at them.
But even if your job is defined for you by others, you can still control how you approach it and how you interact with your boss, coworkers, or customers. If your strengths include curiosity or love of learning, for exampke, you might give yourself the challenge of learning one new thing from each person you work with. If your strengths include gratitude or appreciation of beauty and excellence, then "stop and smell the roses" more often, and remember that the roses include the people you serve, or work with. Identify areas of excellence in other people, and then tell them what you've noticed. When strengths help you build relationships, the payoff is most likely to be long lasting.
If you can think of no way to recraft your work -- if your job feels entirely wrong for you, then you have only two choices: change your line of work, or change yourself to improve your imagination.
Third, consider changing yourself
If you are prone to depression or anxiety then you are likely to be dissatisfied with your job, and with the advice on this page. You are probably thinking about all the reasons why you can't quit your job and can't recraft it. You feel stuck and helpless. If this description fits you, then try to fix your mood problems first. Negative moods narrow our focus, reduce our creativity, and increase our fear of risk. Everything seems difficult, unchangeable, or risky when you are down. Follow these 5 steps for increasing your happiness. In a few months, when your mood has improved, you will discover options that you cannot see now.
To learn more about positive psychology, strengths, and workplace satisfaction, these four books are excellent sources:
Gardner, H., Csikszentmihalyi, M., & Damon, W. (2001). Good work: When excellence and ethics meet. Basic Books.
Buckingham, M., & Clifton, D. O. (2001). Now, discover your strengths. Free Press.
Csikszentmihalyi, M. (2004). Good Business: Leadership, Flow, and the Making of Meaning. Penguin.
Seligman, M. E. P. (2002). Authentic happiness. Free Press.
Also, The "Values In Action" organization, which created the "Signature Strengths Survey", maintains a website that reports research findings obtained using the survey. See "research," then "overview of research."
And finally, if you have not yet read The Happiness Hypothesis, you can read chapter 8 ("The Felicity of Virtue) here. The 24 strengths are discussed on pages 9-11.