For many days, one might be miserable at one's job, and think it is never going to be enjoyable ever again. But then you will have a decent day, or a string of good days, or a series of days that have some combination of good and despicable. The main thing I want to emphasize is that if you are in one of those strings of horrible, deplorable days, keep striving to do your best at whatever it is you are required to do, and remember the times where you were in a streak of horrible days, and how you eventually hit an oasis, or at least a water fountain of refreshment.
Some days will come that will refresh you. Something will happen, you will succeed at something, you will meet someone new or from the past, who will brighten your day, and you have to accept that blessing, and let it propel you through the crummy days. If you are in a rut, it will not always be so. Just don't give up on your life, ever! Keep struggling, keep pushing through, and even if you are not doing perfect, you will know you are doing your best, even in a pleasure-less situation.
No matter how bad things may get or feel like they are, there is always a point where you will be relieved, and be lifted up into something better. Just remember, that when you are having a day that sucks, some days suck.. But not all of them.
Be sure to read more on Joshua's blog, Fullness of Happy.