Some days seem ideal for making progress, except I just don't have energy. Sometimes this is a mental block, but more often it has been simple dehydration. I now keep a log of my water consumption, and if I feel lethargic, I usually see that I'm a litre or two short.
I've heard of people making dental appointments, and then "choosing" to work instead of going. I have a friend who will sometimes skip a party or concert to work, telling himself not to waste such important hours. He is also very fond of lists, sometimes even doing something on the spur of the moment, and then writing it down for the pleasure of crossing it off. However, he also says than every item on his to-do list is really a title for a new list.
BTW, of the homebuilt aircraft that are begun, 10% are finished by the first owner, 10% by the second, and 10% by the third. They then fly or get parted out.
"If it were not for the last minute, a lot of things wouldn't get done."