Sometimes you want to write, to really write, but the ideas just aren't coming. You hop from one WiP to another, you draft out part of an outline, write down a concept, scratch together some character profiles, make notes, scribble on notepads...you name it, you do it. Sometimes though, the idea you're searching for just doesn't come, and nothing else seems to stick. So what do you do about it?
Straight off the bat I'd say that sometimes a book just isn't ready to come out yet. Yes, I do like the maxim "write every day", and I believe that can hold true once you start writing your book. However, you can't force an idea to come out. You need to let your ideas percolate without thinking about them too hard. And I don't mean think of an idea and forget about it. I mean forget about thinking about an idea. Give your brain time to breathe. Sometimes, I believe, if we pressure ourselves too much then we end up writing things we don't enjoy, pushing out words that have no passion, using half-hearted concepts, and not enjoying what we do.
Certainly, there are deadlines to meet (especially those under contract, but any good writer should have set their own deadlines, in my opinion). However, it's easier to edit a book that is written with compelling passion and with a clear goal. Otherwise, you can end up with a book that doesn't say anything in particular. If you don't care about your plot and characters enough, why should your reader?
So my one piece of advice is to sit back, close your mind off from writing, and live for a while. Personally, I take a week or two off from reading, as other books can cloud my head, too, as I'm always thinking about craft when I read. It also really helps to get offline when you can. Stop bombarding your brain and just let it be. You might be surprised what your subconscious comes up with.
I hope this idea helps you, and if not, then, as usual, just take it out of your writing toolbox and replace it with something else instead. Writing is such a fluid, personal, mutating art that there's no one way - there's just advice from one person's point of view to another, and everything's worth a try at least once.
Happy writing, and I hope those ideas keep flowing!