January isn't my 'low' time as far as writing goes (because I have the entire month off work, so it's the time I plan on mad-crazy writing), but even during January, there are good and bad days. But I rarely get to the end of any day without feeling like I've accomplished something, because I count all sorts of things as 'accomplishments'. Yes, some days I write 5000 words, and that's great. Other days I walk around the garden and take some good photos to use on my blog, and that's just as important as the 5000 words. Some days I realise that I'm simply not going to get more out of the tank until I put more in, so I take off for a day hike or go to the beach. I count that as a successful writing day, too.
I'm also really big on my quarterly plans--every 3 months I write down my SMART goals for the next quarter of the year. When I find myself spinning my wheels on some piece of writing, I can look at my goals and choose something else to work on that day, and know that what I've done for the day gets me a step further towards where I want to be.
But then I've always approached writing as more of a business than an artistic endeavour--and I learned from running a heritage interpretation business for 15 years that getting the job done can mean spending a 'work day' in the garden, and then stuffing envelopes all evening, or helping out at the kids' school on a Friday and spending all day Saturday at the computer. It doesn't have to be neat and tidy, 9 to 5, Monday to Friday. Sometimes it's more efficient in the long run to go with the flow, do what feels right in the moment, and know that you'll be more productive overall in the long run.