I have a project I swore I was going to finish, dammit, before starting on a new one. I try to execute on several different small projects every day, along with my professional responsibilities, but the rules have always been: one writing project, one art project, one software project. Since I'm the father of two teenage daughters, frequently I miss one or all of these on any given day, but I've learned not to excoriate myself for skipping a day, just pick up and keep moving.
The problem is that right now I have one software project I'm really not enjoying. I want to finish it, but not right now. At the same time, I have another software project that I know would be fabulous to start with. In the old days, I would have just jumped in and abandoned the old one. I really do have a bad case of Leonardo DaVinci Syndrome, but I'm learning to fight it. Instead, I'm getting a new problem: I don't want to work on the old problem, but working on the new problem would mean abandoning my commitment to Finish.
So neither one of them gets done. Sigh.
[*] I was going to use a more unpleasant term than "blockage", but decided at the last minute to go with something less... organic.