They work in vain who say " if only I get this promotion", "when I finish this project, I'm going to start doing what I really enjoy" etc. Such people are judging their own life through someone elses eyes. There is less difference between doing the right job and doing the job right than most people would expect.
The job to consider quiting is the one you aren't allowed to do as well or carefully as you know how.
When goals are distant from the effort of the moment and couched in terms of "why to do this", it is as if you are in a row boat crossing the ocean. When goals are moment by moment and couched in terms of "what to do" , you are still rowing but now move an ocean liner through a ditch. When goals are in terms of "do the best you can", it doesn't matter where the finish line is as present effort becomes the goal.