One of my least favorite writing excuses is blaming the muse for not cooperating. As if some mythical figure has influence over your writing. I know, it is the personification of the writer within you, but it also a way of avoiding responsibility.
"I can't write today because my muse is silent." But is it really true? I haven't been writing much this summer. I'd like to blame it on some nebulous internal muse, but the flat truth is that I'm lazy. Writing takes effort and I'm tired. It's hot, I'm cranky and I'd rather play Bejeweled than focus on any of my WIPS.
And the muse isn't the only one getting the blame. Lack of time, family commitments, jobs, all of these become excuses for our inability to get words on the page. But really we need to look in ourselves to find the answer. Sometimes we just don't feel like writing. That's okay. Unless you've got a contract, you don't have to kill yourself to meet a deadline. You can slack. But don't blame a muse. If day after day you feel like this, still, don't blame the muse. Take your WIP out and see if it something in the actual story which is pushing you away. Maybe you are out of the habit of writing. Like exercise and dieting, writing takes focus and work. The rewards are slow in coming.
For me, I've just had to put my butt in the chair and write. Sometimes I can only do it for 10 minutes or so. Some days those words flow easily, some days, not so much. On Tuesday I managed to get 600 words written for the entire day. Yesterday, I got 450 written in less than an hour. Accept the fact that your creativity needs to be forced and do what you can.
You are in control. You are the creator, not some mythical entity in your head. If you wait for the muse, you will be surrendering the fact you are the one in charge. You may have to change the way you approach your writing, look for new tools to get you on your way, but ultimately you will be more productive.