I love this concept. It of course means doing something every day that contributes towards your goal or ambition.
To me it applies in the following way:
To really reach a high level of competance in a short timeframe one must feel an urge to learn. In a way similar that many use social media, searching for a sliver of excitement, hunting through different information sources.
The point is (as these screen time apps have shown) a little often can add up to a lot at the end of the week. So even on a full day at work there are a bunch of opportune moments to learn.
The most important thing to me is the mindset, that it doesnt feel like homework.
As well as NO ZERO DAYS, here are some other principles I abide by in my current profession.
Very little skill is to be gained just by watching.
The fundamentals must be in place first to enable future development.
Develop true understanding rather than enabling memetic behaviour.
Improvement is sometimes a delayed reaction rather than instant revelation.
Variability in the process keeps attention levels high.
True ambition and defined needs/goals speed up the process.
Role models can be inspiring.Learning is unpredictable.
The right environment/culture is a massive help.