I remember my first 10k race. Prior to that, the longest distance I ran was 3km. Tired 3kms. But I made it through 10km on sheer race-day adrenaline and perseverance.
And then I started to read running books, blogs, forum, whatever you have. And I started to do all the right running things - speedwork, hill runs, lsd, tempo runs. And that's when I found out that it's sort of impossible to do a 21km without training.
But at the same time I know of some friends who jumped into the 21km race without proper training, that I know of. They did it again this year for BIM with minimal training that running blogs would have a heart attack on upon finding out. One dude even did the full marathon and I think the longest LSD he did was 18~ km. He finished.
In 7 days, I'm going for a 21km. I'm freaking out because everyone says it's not easy, especially the last 7k part. Mentally mostly, and your body takes some toll on it too. My serious lack of preparation as stated by all these running blogs and magazine is freaking me out, bit by bit. But on the other hand I'm trying to remember these set of friends that ran 2 half marathons with just hard motivation. They didn't know that running without training was suicide.
I'm just going through with it. I wouldn't know how hard it would me on the race, but I'll try my hardest to finish it, whatever time it takes.