It's is obviously an abused cliche, but to be productive you have like things you want to be productive at. If you simply hate your job, you will not be productive at it.
This goes without saying and it's been said time and time again by almost every imaginable motivational speaker; from John Scherer to Steve Jobs.
My problem has always been that only the children of rich parents who can afford to try to be artists can really take advantage of the insight this "truth" grants. Everyone else might have a job that they like, but really there are things they like a bit more than that job.
If you want to be productive, you have to manufacture that "click". For me, the fundamental problem with lack of productivity has always been what I like to call the "depressive cycle". I don't feel like doing something which makes me feel bad about not being productive. The worse I feel, the more sorry I feel for myself, the less likely I am to get it done... And if I don't get it done... You get the point.
So, my trick is to embrace the feeling of satisfaction I experience when I get something done. And use it as a motivation to get something done. Essentially, the more productive you get, the more productive you become. What might work in this situation is prioritizing your tasks in the order that gets you going. I'm still experimenting with that. If it gets me somewhere, I'll report that here.