When you’re dead beat, there’s zero motivation to work on a project. It happens a lot after the day job for me. There’s not a lot you can do, but even a little effort can get you to the metaphorical—or actual—drawing board.
And that’s what you want. A page a day gets you a novel in a year. A line a day gets you several paintings, or a series, or a lot further along than you would be waiting for fresh energy, a full work day, or the lightning strike of inspiration.
A piece of something every day is you putting up a lightning rod.