It's nice to be able to draw what you want, but sometimes when you're in blocks like that you're only choice is to just sit down and force yourself to draw.
Sure, it might create uninspired, generally bad artwork but maybe that's what you need to start doing better, to get all of the crap out of your system. Bad art isn't necessarily a bad thing, and more often than not bad art is better than no art at all.
At least with bad art you can see what you need to improve on. If you have nothing to look at then you'll have no idea what you need to do.
Updated by anonymous