Whichever the case may be, there are a variety of things you can do to try to get your writing routine back in gear when it feels like it's not where it should be. Here are several of the ones which I would personally consider using at a time like that.
- Change Your Physical Location -- One of the things I've noticed is that when I make a point to actually go somewhere (library, coffee shop, etc.) to write, I typically end up being particularly productive. For me, I think there are several reasons for this, not least of which is the fact that those writing sessions tend to be longer than average. But it's also a psychological indicator to myself that "this time is for writing" and not for anything else.
- Write Something Different From Your Usual Fare -- I've written a whole blog post about some of the benefits of writing something different than what you usually write. If you're struggling to get words down, particularly if you're feeling that what you're writing isn't "good enough", then you could use this as an opportunity to write something with no expectations of yourself other than getting new words down.
- Set A Specific Short-Term Goal For Yourself -- Be careful, as this can be a double-edged sword. If you set too ambitious of a goal and don't meet it, you run the risk of reinforcing negative mental narratives. But, if you set a goal which is challenging enough to make you feel as if you've accomplished something significant while also being reasonably attainable, it can give you an opportunity for a short-term "win." Bear in mind that goals are best when they revolve around things entirely within your power. Setting a "goal" of having a story accepted by a specific magazine isn't something you can completely control. That could be an "ambition", certainly. A better goal -- one that's entirely within your control -- would be to plan to write a new story aimed specifically toward that publication and submit it there within the next month.
- Find Productive Tasks Related To Your Writing Which Aren't "Writing" -- Setting aside for the moment notions specifically of "writing every day," there are plenty of writing-related tasks which need attention. Perhaps you have work which you are circulating to publishers in general but which is not currently out on submission. Then get it back out the door! Maybe you have promised to critique a story by someone else but haven't done that yet. Use some of your writing time to get the critique written up. And so on. These aren't necessarily glamorous things to be doing, but if you get them finished, then you no longer have them sitting out there needing your attention "sometime." And maybe that "sometime" will be a time when you have an especially productive writing day.