The suggestion was that, if you really really really don't want to go running some day, try to only shoot for running a fraction of the distance you would have, so that you reevaluate the choice of running the second half once you've already run the first, the idea being that you'll probably be much more in the mood after you've got started.
Not a really strikingly original suggestion, but still. Though I've heard things like it a lot over twenty-few years of being a nigh-incurable procrastinator, this version, the image of running specifically, is of late stuck in my head somehow.
And so I've been trying to force myself into the exercise of writing a little (non-LJ!) writing every day since mid-Mayish, making it nonpublic so I can actually write fiction (or, god forbid, verse) without cringing over every word, and the thing that amazes me is how, if I can write just one sentence, I can easily write a few hundred words, now and then 1000-1500. But getting that first sentence is hell. Weird.