The motivation to train for training

I've decided to begin training for the marathon in June, 2010. Well, I have begun training to prepare for the inevitable training that will launch in approximately January. I still haven't signed up. I'm extremely nervous to commit to such an event. Will I be able to run such a distance? I don't know. So many people have done it before...why wouldn't I be able to? (That's what I tell myself about being in labor too...why am I thinking about having a baby when I'm not even dating anyone? I'm not quite sure. I generally chalk it up to the estrogen.)

I'm afraid that this ephemeral state of motivation will quickly dissipate, and I will discontinue my regimen, all the while making stupid excuses as to why I can't/don't have time to run. In yoga, I always tell myself how much more strong and capable my body is than I think it is. I now wonder if I believe myself because I'm pushing my limits for only about an hour and a half of my life at a time. Training for the marathon would require that I tell myself this daily for 18 entire weeks. Does that sound like a lot? There are 52 weeks in a year, which mean that's about 9/26 of the calendar year...and that's about the best math I can do.

My dad told me to just say "YES" to the marathon. I'm saying that now. I'm just already disappointed in my(future)self for quitting. Without truly beginning. That is whack. Words of encouragement encouraged.