Well - I only went and bloom in' did it, ha ha!
I was a little nervous before the run started, for some bizarre reason. Once it started, it actually felt ok - I tried to think of everything BUT the fact that I had 20mins of running ahead of me! Listening to my own music really helped, as I found myself silently singing along to the words, which distracted me a little from what I was doing. About 8mins in, the gremlin on my shoulder started to make me doubt. But I tried to focus on how I was feeling, physically, in that moment, that I had a pattern going with my breathing and a rhythm going, and that my legs felt ok, and it made it easier, because I felt fine. Finished with a big grin on my face, and then my legs felt detached from my body for the warm down!!
For all of you who have it to come - if you have done all the work leading up to it, then you can definitely DEFINITELY do it, so don't doubt yourself!