A deadline is useful only if there are tangible incentives attached to it, and it's rare that you can self-impose these kinds of incentives in a way that isn't

A deadline is useful only if there are tangible incentives attached to it, and it's rare that you can self-impose these kinds of incentives in a way that isn't self-flagellating. My advice is to let go of timeboxing and let your sense of wonder, exploration, and discovery guide your progress.