It's hard to be concise about it, but I'll try.
A main concept I have in mind when learning new things, no matter whether it's a language, physical exercise routines, or an instrument, is "micro, macro, meta".
Early on in my life I didn't have concrete words for these, and I'll explain what I mean by each. To me this isn't anything special, mind, and it might be extremely obvious, although based on conversations with friends and family, it doesn't always seem to be.
Micro: The fundamentals and specifics of each activity and skill. For piano, for example, it would be concepts like "where are the keys", "how does the sound differ with pressure or speed", "how does rhythm notation work", etc. The micro often has immutable principles: A specific muscle _will_ have a limit (even if that limit changes over time). Piano sheet music notation's structure works a specific way and the rules for existing sheet music is inflexible. It is often as close to "fact" as you get.
Macro: The application and combination of the micro skills. Hitting keys in the right order to make a pleasing tune is a macro skill using a string of micro interactions. To hit a key at the right rhythm, with the appropriate force, is a macro application of the micro skill of knowing what key to hit based on the notation or memory, and the learned and practiced macro skill of rapidly applying varying force.
Meta: The often surprising connection between disparate micro and macro concepts from seemingly unrelated activities. Keeping a subconscious rhythm, something I learned over time whilst playing piano -- first using a metronome, then counting out loud, then internalizing it -- is also useful when exercising or when meditating, because it helps you more effectively align different muscle groups and tendons in unison when, say, doing hand-stand push-ups, or breathing exercises to force your brain into a relaxed state during meditation. Keeping an internal rhythm that can "beat" separate from your heart and external stimuli makes so many physical acts easier. But conversely, having a body that is used to various body parts acting in unison to a beat makes playing the piano easier as well.
The meta aspect is also observing myself as I'm learning new skills. Listening to when I get frustrated or lose motivation, and analyzing why. I learned early that losing interest didn't mean I'd lost interest in wanting to get good at the activity itself; it simply meant I was hitting a specific wall in the micro or macro, and I needed to change my approach. This is a key insight: I was told by teachers that when I lost interest, I just needed to "focus and apply myself". But it felt _wrong_ to force myself to repeat something that felt like it was going nowhere. When I realized it was my brain and/or body effectively telling me "we're going in circles by repeating this right now", all it took was to change the activity. For example when learning Japanese; when I hit a wall during kanji memorization study, I'd shift focus to how I could combine the kanji and kana I knew into sentences, and test it out. The next day I'd usually be much better at kanji memorization again. If not I'd shift to something else, like re-reading the literature on language structure, to give myself macro applications of the micro specifics.
These three concepts are something which my focus will flow between as I learn something new. I'll often ping pong my focus from day to day between micro and macro, while always being conscious of the meta aspect. And the interesting thing to note is that as you get good at things like the piano, often macro skills turn into micro skills as the brain and body optimizes memory and nerve signals. For example, playing a sequence of notes at great distance that requires one hand to jump between distant keys while the other is playing a steady tune will at first be a series of micro skills executed in order, slowly, as part of a macro series of maneuvers requiring great focus. But over time, it becomes a micro tool to skip all of those keys without requiring any focus at all -- in essence what we often call muscle memory, although it goes deeper than that.
Finally, I'd say that for the brain and body to most effectively optimize learning, it needs constant reinforcement, but it doesn't need to be for long. You just need to indicate that this activity is the new normal; then the body and brain will go out of their way to optimize so that it becomes easier and easier to do, expending less energy.
When I'm learning something new, some days I might spend a lot of time on it. But many days I'll spend fifteen minutes, and that'll be that. Life gets in the way, but usually not so much that we can't spend fifteen minutes at _least_ every other day or so. Even five minutes is better than nothing. It's enough to signal that this is the new normal, so best keep optimizing for it, because we'll keep doing it until it's cheaper energy wise.