I'm having that problem with the story I'm working on...

Perhaps move on to a different piece for a while? Or put on some music that really puts you in mind of whatever it is that you're supposed to be creating? That sometimes works for me...

My problem is if I have to come back to something at a later time, my art style changes. You can really see where it looks like 2 or more people were doing the same art just in different sections. So it's one of my rules to finish something first that way it doesn't look like it went through a blender. Haha :p

That makes sense actually... :/