It's easy to get impatient, but chances are that we have simply shifted from one kind of creativity to another. (In my case, it has been studying animal communication and working with my own dog, Quincy.)
Perhaps, it was time for something new, but now I'm getting a little itchy and indeed feeling like my illustration! I don't even want to try the activities I know of for getting going again....but, if you do, here they are:
Change your media, change your tools, look at lots of art, and exercise your body.