What's in a goal?

I am now 5 days into my somewhat serious training phase for my first marathon. I say its somewhat serious only because I have yet been able to commit to a healthier eating habit. I have sat down with a friend and he has helped me outline a training program to accomplish my goal. The training program officially starts in June which is suppose to give me 18 weeks of training. I keep telling myself that all I want as a result is just to finish which is how my training program is set up. The problem is the Marine in me keeps whispering "that's not enough".

 Its interesting to note here the difference in perspective of what I am used to compared to my current program. In the Marines we over trained, I guess is how you would put it. That is to say when the company commander and/or battalion commander wanted to do a run we would go for a longer distance than we knew the company and/or battalion run would be. This way we were certain that we would not only make it but not look bad doing it (not good to show your butt in front of the boss right?). The idea was bleed in training and sweat in battle. 

 I hope I'm not sounding to ungrateful for the help my friend has giving me cause that is not how I feel or mean to sound. Any and all advise is welcome since my idea of training as you may remember from previous posts is to walk out the door start running and follow my nose. Run up hills, trot down, run some sprints when you can and that was about it. Seemed fine and that sort of hap hazard type of training gave me a 2 hours and 4 minute finish in huaraches for a half marathon last year. Last year was mostly huaraches running. This year I'm aiming for barefoot. As much as I can. There is no real reason, just to be non-mainstream I guess. I never did like to be like everyone else. Although I must say my injuries have been less since I started running minimilist and barefoot. So my first marathon race will also be my first barefoot marathon.