The first and most important thing to understand is that everyone goes through a rut in their career. It does not matter what field you are in, eventually you will get a little bored or you realize that you have already faced the challenges which will be offered to you. Everyone wants to feel that they are contributing something significant with their lives and time. If you do not feel like this then it can be extremely hard to make yourself continue with the same old. So, if you understand that feeling, it is now time to evaluate the reason for your career rut: is it you or the situation you are in? This will determine the next steps that you take to get out of your rut and feel rejuvenated.
If you decide that it is a personal issue, then there are a few steps you can to take. Many people leave their vacation days to accumulate, so take advantage of your time off! Go on a trip, even if it ends up being a staycation, just allow yourself a good break from the office to rest and get your energy back. You can find ways to change the makeup of your days to liven the workweek grind. Try adding an exercise class during your lunch break or see if you can change the hours you spend in the office. Anything to mix up your normal routine and make things interesting again or give you something to look forward to.
If you decide that is a situational issue, then it might be time to look at a new job or redefining your position in the company. In some extreme cases you may decide that you need to switch careers and are just not feeling satisfied with the field that you are in. Any decision you make, the goal is that you get out of your rut so that you can tolerate all the facets of work once more: the unrealistic demands, impossible odds, etc. Essentially the things that make your job difficult, but rewarding and fun!.