I gave up three years ago in week 5 and am starting again (I'm on W2R2). I'm very unfit, and very overweight - so find every single step unbearable. I literally have to think 'just make it to the bin, then decide if you want to stop', then 'just to the bench, then decide'.... the whole time.
BUT - signed up to a 10k race in September, so kind of have to keep going. I really don't want to quit.