I think, no matter what, it's important to stay busy. Not crazy busy, but definitely active. Don't get me wrong: I love taking a day off now and then, and sometimes all I want to do is drink a beer and watch TV. But I guarantee you that J.K. Rowling never looked at her career and though, "You know, I wish I hadn't missed all those episodes of Downton Abbey." (NOTE: I have no idea what she does or does not watch on T.V. I'm just picking people and shows at random, here.) Sure, there are great shows out there, and they may be very inspiring, but if the option is either write a chapter in your book or catch up on America's Next Top Model, which one is going to bring you closer to your career goal?
Recently, I've discovered that when I'm staying busy, I spend more time on my writing, even if I'm spending more time on my day job, quality time with my wife (even though that isn't taking up NEARLY as much of my time as I'd like due to our schedules), and even my new hobby of homebrewing.
This isn't to say I'm more motivated than ever. In fact, my motivation is on a more intense roller-coaster than ever. There are days when I'm excited to get up and write as much as I can before work, and then I get home and want to get even more writing done before bed. But there are many days where I just want to sit around and just forget about this crazy writing dream.
But those tend to be some of my more productive days when it comes to the quality of writing I get on the page.
I guess my point in all of this is that proper time management plus determined focus can often times make up for a lack of "motivation." Those times when we feel like giving up, or we just don't care that day. Focus is what's needed when we don't "feel" like it. And with focus, we develop the necessary time management skills to build the DETERMINATION to move forward, especially when the motivation just isn't there.