In his book So Good They Can't ignore You, Cal Newport has identified certain work practices you can employ to ensure that you stay motivated at your job and ignite a passion for it, even if it isn't your dream career.
Invest time in your vocation. Although talent is essential when it comes to succeeding in certain professions (no one can hit a one-handed backhand like Roger Federer no matter how much they try), working consistently at one place and working towards excelling at whatever it is that you do will eventually result in your being extraordinary at it.
Focus on quality. Instead of asking yourself "Is this job right for me?", shift your focus towards producing error-free and well-researched work within specified deadlines. This is because irrespective of the industry you are in, career success (which has been linked to job satisfaction and increased productivity) - and your professional reputation - is more often than not contingent on not compromising on work quality and your work ethic.
Learn to love what you do. If you have not been lucky enough to be able to pursue your childhood passion as your career (and most of us have not), conduct an introspective analysis to identify the aspects of your job you enjoy and which ones you find mundane. An important factor to consider is that the more time you spend honing your skills, tasks that seemed complicated initially, become easier, more enjoyable and less stressful.
Once you invest time in your work and focus on the quality of output, you will more often than not learn to love what you do. Not only is this good for your general well-being, doing so you will help you acquire career capital, which in turn will result in you acquiring skills and competencies - above and beyond those specified in your JD. In this way, you will become a valuable resource for your employer as you will be able to perform a variety of functions.