I took out the ‘Top' from this ‘Top Ten' because I think this sort of thing can be quite personal, and your happiness at work can be a result of very different things.
However, this is still an excellent list of some simple ideas that should make your work-life more pleasant.
Practice Professional Courage
If you are like most people, you don't like conflict. And the reason why is simple. You've never been trained to participate in meaningful conflict, so you likely think of conflict as scary, harmful, and hurtful. Conflict can be all three; done well, conflict can also help you accomplish your work mission and your personal vision. Conflict can help you serve customers and create successful products. Happy people accomplish their purpose for working. Why let a little professional courage keep you from achieving your goals and dreams? Make conflict your friend.
Top 10 Ways to Be Happy at Work – [About.com]