I will confess that part of my difficulty is a certain level of laziness and lack of discipline, which might come as a surprise to those who have admired my level of output over the last few years. My problem is that I want to jump right into the business of writing interesting scenes, actions, and dialogue, which is much more fun than painstakingly figuring out how the story should be built. The trouble with a patchwork approach is that often the pieces don't end up fitting together nearly as well as hoped, and one is left with either a narrative that jerks along like a train over crooked rails or with a tedious task of rewriting until some level of harmony is achieved. Sometimes the kindest thing one can do for oneself is to put the entire mess out of its (and your) misery and to begin writing a chapter or even the whole blamed book again from scratch with at least the hope that the ideas you've already had will keep percolating in the back of your mind until you find a point at which they may actually do some good.
I'm not nearly at the point of needing to take such a drastic remedy yet. The problem is more psyching myself to exercise the discipline to build the needed framework. As with many other life projects, attending to the basics isn't much fun. But it is necessary if one is to get to the fun parts.