I've liked the Big Plan idea ever since I first heard of it, even though I'm not doing classic AVRT. My view is that when we fail, it's not really the plan that fails... it's really just a wish, a decision, or a goal. It's our implementation of the plan. The actions that are meant to keep in line with the plan. Accordingly, my suggestion would be to tweak the implementation part, what sort of things you do to stick with your plan in the long run. When sober, I'm quite a strategical kind of person, like to think about long term goals and projects... in this sense, the Big Plan for me was the aim of the project and then I need an approach, methods to work on it. So when I think about failure, to me it's like the actual approach failing, not the aims/plan.
I've been successful with the "sobriety project" since I got into it, but have had numerous other personal goals and aligned approaches that did not yield the wanted outcome. So I need to modify the approach. Often it does not mean rejecting the original one completely, but adding to it, or trying in a different way.