Make it work for you
I think there might not be a more foundational lesson than that whatever it is, you have to make it work for you. Every skill that you learn, it has to be hand tuned to your own style. It must be impedance matched, by you, to your own mind and abilities and preference. Maybe that's called mastery, or maybe it's just learning something and owning it, I'm not sure.
This is not to say that you should completely reinvent the wheel with every new skill. Take from what others say the skill is; learn from that example. But then adapt it to your own web of skill and abilities, which does require some inventiveness of your own. It's a critical step, never stop doing this.
I'll give a couple of examples.
When cutting vegetables for cooking, and I'm just an amateur at this, there are a few things to remember. The things to remember increase with the level of skill you bring to it, but so does the automatic recall from practice. How to hold the knife, it's particular to your hand. I've found that it evolves over the years, as your hand ages and wears, or your strength changes. Hard vegetables like carrots take a different grip than soft ones like tomatoes or potatoes, which have their own particular needs. Cutting them evenly is another kind of attention. Remembering to treat each of these aspects of the skill with care is it's own skill too. You can see, there is quite a lot here for this practical kitchen skill.
Going to a more abstract skill, I'll talk about algebra. I don't use it day to day anymore, but I've had quite a lot of practice at it and it is a language I am fluent. There is skill of noting which variable is of interest, and not losing track of that. There are the operations of moving around the different variables. Not losing a sign or constant as you work down the page. Expanding and simplifying, it's not so much the operation but how you execute it that is the skill. This is what I mean by making it your own. Others will perform the same operations, but they have there own mnemonics to help them, or little rhymes or what have you.
The same is true of all skills. Some you may become so fluent at that you don't even see these little adaptions that you, yes you, invented to make them your own skills. But they are there.
And when you learn a new skill, even if it's been years since you have done so, you'll have to invent new adaptations to learn the skill and make it your own. It's one of the steps necessary to add it to your own network of skills.