For me, it depends on how much I understand the project going in, or how much I think I understand it. The biggest non-work project I've done recently (other than Benjamin) is the kitchen, and that started with some research, some machinery purchases and a lot of CAD work before I even got to making any sawdust. At every stage I had a pretty good handle on what I had to do, even though it's taken much, much longer than I anticipated. I think what made it work for me was strong intrinsic and extrinsic motivation: I love woodworking, and my existing kitchen was horrible. :-) At one point about halfway through I sat down and plotted out the entire rest of the project step by step, which helped a lot in tracking my progress.