I've been writing things in one form or another for about 13 years, and I've passed the first "million bad words" every writer's said to have. I've also released around 200 rap songs under different names, which tends to come off lower-status but is no less dear to me. (I would consider 500-1000 songs to be the equivalent "bad" cutoff, though.) Since these are the things I've spent the longest time learning and practicing, I want to see if I can apply anything in them to learning and practicing in general. Here are my thoughts so far:

• Every art is really several arts. There is no "learning to write" separate from learning characterization, imagery, the elements of style, dialogue, text formatting and so on.
• Likewise, these sub-skills are not all created equally - while content, rhyme scheme, flow, swing, breath, cadence, delivery and so on may be the most relevant to other musicians critiquing your work, the final judgment of what you make can depend on things that seem at first to be unimportant or polish, like the technical specs of your microphone or the level of audio engineering performed on your finished product.
• Attainment individuates. Rank beginners produce things that are very alike because they're making the same handful of beginner mistakes. "Beginner mistakes" themselves are just how humans natively do things, and it's only in overcoming them that the wider space of possible performances is opened.
• Because of this, skills and techniques are generally about iterating away from whatever your earliest work looks like, one step at a time. And from wherever you're standing, it's possible to identify someone as being more or less skilled than you. (Someone it's hard to do this on, who seems better at some things than you are and worse at others in a way that's inconclusive, is basically level with you.)
• You can give more advice to one student than to all the students in the world, and most advice is written for as many of them as possible. 1-on-1 lessons with someone you want to be more like can be worth more than all the articles or books you can find, if you're able to truly accept how many things still need improving.
• To reemphasize: the person who teaches you must be someone you want to be more like. Not all advice is instruction in how to be more like the advisor, because people can recognize and speak about their own flaws more easily than they can fix them, but you should expect to wind up more like your teacher than if you hadn't studied under them.
• When it's said that those at high skill levels are "never done learning" it's because they've achieved a higher granularity of what they can improve.
• Early work is typically bad even to you, which can be extremely frustrating, but after enough practice it's possible to be impressed by your own work - especially if you've left it for long enough to forget the details of it. Despite this fact, impostor syndrome never really goes away, it only adapts to your new situation.
• Arts produce communities of practitioners. The majority of these people will be worse at what they're practicing than you'd expect, because they fall below the skill level usually presented publicly. At first you may not recognize that you're one of these people, and that your work is not so great either.
• Because of this, spaces practitioners use will typically sprout a policy of giving as little criticism as possible.
• This is not necessarily a bad thing; criticism is not a panacea, not all of it is worth following and there's only so much of it you can act on until you've internalized and digested it. Plus oftentimes people really do just need a bit of social encouragement so that they can continue forward. (This goes doubly so for anyone who makes things for free.)
• There's nothing wrong with simply wanting praise, but know that's what you're looking for and don't confuse it with a desire to cleave off your flaws as fast as possible.
• The more work you produce the easier criticism will be to take, because you identify less with the thing being critiqued.
• The practice of creating something is really the practice of making very small moment-to-moment decisions, usually between the handful of ideas that arise in your mind about which thing to do next.
• As you notice the flaws in your own work and the work of others, you'll eventually notice flaws in the work of those you admire, including the ones who inspired you to begin in the first place. The end result of this isn't dislike of your past heroes, but an understanding that they really were just like you are.
• Beginners should aim to use or dismiss as many of their ideas as possible, because better ones will appear given space and attention. Your ideas and insights into what to do will never be worse than they are now, and future ones need room the present ones are taking up. Be less concerned about running out of ideas than with the quality of the ones you already have.
• The simplest way to encourage ideas is to write down each new one as soon as possible from when it enters thought, especially the ones that are no good. This both keeps the way clear for better ones and encourages your brain to generate ideas continuously.
• Doing something well and doing it well in front of an audience can be completely different skills, and sometimes your feeling that you're good at something will completely dissolve once a small group of strangers are watching you. (When I attempted a small concert at a convention the songs I thought I could repeat by heart were suddenly so foreign to me that I had to read them off of a phone.)
• Likewise, there are things which may seem as trivial or "part of the package" which no amount of normal mastery will teach you, and the only path to these is to learn them separately. (The easiest example of this is freestyling, which I can't do to save my life despite it being the first thing anyone asks for upon hearing that you make rap - to develop it, I would need to start fresh with the skillset involved, which focuses more on quick-wittedness and knowing precisely how much to extend oneself.)