But there is one simple piece of advice (and this goes for most anything) is to make a habit of doing something daily.
Yes, even writing.
I'm in the middle of reading Robert Jordan's Wheel of Time series (yes, all fourteen books plus a prequel novel) and in looking at the publication dates, that man had an impressive writing output. Another fantasy author I admire is Brandon Sanderson. He can churn out the novel behemoths at regular intervals. Yes, I'm still waiting on a few other fantasy novelists to finish their series . . . Martin?
What does this mean to me? For the past month or so, I've had a few setbacks, which has eaten into my writing time. And because of it, I find myself taking longer to get back into the story. This could be the reason why George R. R. Martin is taking so long with finishing his monumental series, simply because he has written other things in the meantime.
I'm not comparing myself to Martin by any stretch of the means, but when you're busy with other obligations or distractions, it's harder to get back into the story. I've had to go back to the beginning of my latest novel three or four times now to re-read the whole damn thing--I've enjoyed reading it, but for crying out loud I just want to finish it.
The same goes with exercise or any other habit. Do something daily. Even in little drips. You'd be amazed at what you can accomplish.
