WooHoo. Did it.
Having had a wobble on run 2 I can definitely recommend failing . When you know the disappointment of not quite getting there, you're much more motivated to get on with it. A lot can go through your head in 20 minutes but, for me, thinking that I'm going to feel rubbish for the rest of the day if I don't finish is a real motivator.
Anyway failing is only failing if you don't learn from it!