It's important to have a pile of junk next to your work space. It doesn't have to be huge, just little bits of this and that. They can be related to your primary artistic goal or not.
When the creative slump comes, dip your hands deep into the pile of junk and just start putting things together all willy-nilly. Work for minutes, or hours, or days—however long it takes. It's a little like hitting a reset button.
After a while, your mind and body will find a rhythm again. Then you can decide whether or not to go back to your original project or continue with the junk masterpieces that you've been creating. Either way, you win.