I once had a recruiter tell me something that, at the time, I thought was hogwash but which over the years, I have come to understand it was a valid point. The recruiter said to me In every job you ever have, the best you can hope for is two out of three; you will like the job, you will like the people with whom you work, or you will like the location where you live/work. A combination of any two means you are doing pretty good.
For the most part, that's true. Most people find it's two out of three. If you find yourself in a situation where you have three out of three, consider yourself fortunate. If you are only managing one out of three, you might need to consider some changes. Satisfaction isn't something that is guaranteed to last, either. You might like where you live/work, like what you do in your job, and even like your coworkers and then a layoff or merger occurs and the staffing gets shaken up. You suddenly find yourself working with different people or a different boss and they may not be such a good group. Or your job scope changes and you suddenly have less responsibility which leads to boredom or you have too much responsibility which leads to burn out.
Most people I meet who are looking for a new job are looking for more challenge or a higher salary. A growing portion of new clients need to find a job in a certain location due to family considerations such as aging parents or health reasons so they are looking to make a change. Rarely do I hear I just couldn't stand the idiots around me! but then, since that's not really a PC thing to say, I'm not surprised. It happens, though. You spend as much if not more time with your coworkers than you do with your family so the need to get along well is a key factor in employment satisfaction.
So how are you doing? Are you achieving two out of three? What is making you unhappy? Is it time for a change?