I hope you realize the irony in imagining yourself failing at the imagining yourself failing exercise.
If imagining a failure brings akrasia, what's wrong about imagining oneself failing at doing undesired things?
The dangerous thing is imagining oneself failing at things one wants to happen.
the video
I'm posting this because akrasia, procrastination and willpower are often discussed on LW. I haven't read the book, but for those that are interested "The Willpower Instinct" and "Maximum Willpower" are, from what I can tell, exactly the same books.