The taper continues and I feel less confident than ever

With less than two weeks to go until race day, I feel like it is all unraveling. This is not the way I had hoped my training would conclude.  Last year, I felt strong, ready. This time, I was feeling better than ever right up until the final 20-miler. It was a bomb from which I have not mentally recovered. Physically, I guess I am doing alright - my four-mile runs have been at around a 6:45 pace and my 13-mile run on Saturday was at a comfortable but relatively slow 7:21 pace. I know I should not be targeting marathon pace on my long runs, but I feel like I need the work; like I have not sufficiently trained, despite all the effort I have put in thus far. Simply put, I am nervous. The Gansett Marathon on April 14 will be my sixth so I should be over this feeling, but the jitters keep on coming.