I used the Customized Training Program through Jeff Galloway and I can't say enough good things about it. It helped me finish my first marathon/first Dopey strong and healthy. I maintained my planned intervals for virtually all of the races, including the end of the marathon when most other people were exclusively walking.
Also, my stress level pre-race was insanely low. I am an overthinker and I tend to freak myself out with "what if" scenarios. But over the past 6+ months of Customized training, I developed a level of trust in my coach (Chris Twiggs) that let me say "I'm just going to do whatever Chris tells me to do" and stop worrying. On Saturday, when I started to worry about Sunday's heat, he reminded me to follow the plan, which I didn't want to hear but was 100% the right call. He also worked through my new list of "what do I do if's" so that I wasn't trying to make decisions on a foggy runner's brain.
I know that people have issues with the long runs at the end of the Galloway plan (20, 23 and 26 milers), but I went slow as recommended and was 100% recovered within a day or two on the 20 and 23 milers. The 26 took a couple additional days, but the confidence that it gave me on Sunday was worth it. When I started to hit the wall around mile 22, I told myself "it'll be fine, you've done this once before," which was the boost that I needed at that moment.
I struggled - A LOT - with my training plan decision, but looking back, I know that I made the right decision.