When work slows down and I get these stale patches, I set myself "limited time challenges" which could be for a day or up to a week depending, to make me both work harder and think more.
This could be in terms of a shooting projects i.e. only take images of pairs of people, people using phones or left handed only widgets, you get the idea. The projects are selected by randomly open a magazine page and using the first picture you come to as the project basis, so do be careful about the magazine you choose to open...............................................
Alternatively use only one lens for a period, preferably one you've not used in a while, this can be really tough at times especially at the shorter focal lengths. Your back will also thank you for this respite period of not lugging around all your kit.
Another I use is, so many images to be taken by certain times of the day, you note I use the word images to suggest that they have to be both well composed and technically correct as opposed to rushing a couple off to meet the deadline which is of course cheating.
I hope my thoughts may work for you.