Running: Gut check

I'm running the Marine Corps Marathon next month. I've never run a marathon (26.2 miles) before; in fact, my longest run to date is 16 miles, and that was several weeks ago. My training calendar tells me I'm supposed to run 20 this weekend - how that goes will play a huge role in how I'm feeling going into the marathon. I know two things for certain: (#1) I haven't been training nearly enough, and (#2) I can run farther than I think I can. Steve Prefontaine once said that he didn't run races to see who was the fastest, he ran races to see who had the most guts. In that spirit, I'm counting on #2 overriding #1.