Like a lot of people, I used to think I had to be in the mood to write in order to create anything good. And that's true, to a certain extent - your most poetic or heartfelt words will come when you're caught up in the moment. However, there's quite a lot you can do when you're not "feeling" it, and sometimes doing those things can help spark the mojo to life.
1. Research is a necessary writing-related task that doesn't require "the muse."
2. You can look at covers in your genre and get ideas for yours.
3. You can outline the next couple of scenes.
4. You can write a bare-bones draft of a scene and come back and add the heartfelt bits later.
5. You can proofread segments you wrote previously.
See - there's still all kinds of important writing work you can do even when the muse isn't speaking to you. The important thing is to keep forging ahead - she'll come back. I promise.