Find something else to do at work that you get enjoyment from. I have found that volunteering for small projects working on things that I love have helped me to keep my interest at work. While there are many tedious things about my current job, I have found that these little projects have helped to bring my passion back even with the tedious things that I do every day.
For example, I'm working on a small documentation project, volunteering to help with some open-source items, and helping to run a small PoC with my systems administrations skills. These things only take maybe an hour or so a week. But after doing a bit of work on them at the end of a really frustrating day or at the beginning of a really nasty day helps to restore the passion that I have that is one of my strong attributes so that I can bring that passion back and overcome the other things that have sapped my strength.
Find what it is that you can do at work that will restore your passion - it's amazing how a little bit of volunteering will bring your spirit back for you.