The trick for me is always just getting started. Once I actually get over the hump and start working, I generally find it's pretty easy to keep going. It's getting started without sidetracking myself that really puts up the biggest resistance.

That may not work for an author who's lacking inspiration, but in my case I found that when I sat down at the keyboard to work on my book, if I couldn't think of what to write I'd just start writing utter crap for a while until it started to flow a little better, then I was usually off to the races.

Note that Chandler's approach very specifically did not involve getting a task done. He was talking about writing novels over the course of months or years, not little things he was putting off.

Also it's a task where inspiration is involved, so if he forced himself to write every day no matter what, some of it would be worthless because the ideas weren't there. The point of his approach is to make habits that ensure you accomplish something in the long run, regardless of whether you get something done today or not.