One thing I impress upon new developers is to start keeping a blog to journal their discoveries. I’ve been keeping blogs now for over a decade, and I’ve found them incredibly helpful in my growth as a person and a developer.
When you’re working in a knowledge/thinking job, it’s hard to get a sense of how your mind has evolved through the years. Your mind can lie to you, and tell you what you want to hear at that time. “I’ve lost my edge” or “I’m 100 times smarter now than 2 years ago” are things you can deceive yourself with, but with no actual benchmarks in thinking it’s unclear if that’s the case.
Writing about technical matters is a bit like standing against a wall, and marking your height with a pencil. What you thought of as ground-breaking one year (“there’s these things called pipes!”) can be seen as a stepping stone to later things (“Here’s an in-depth look at the kernel build system”). With some deep thinking put into it, you’ll also start to notice the subtleties and implicit arguments in various systems, and those little notes will become a message in a bottle for someone else.
If you write regularly, you’ll also see your writing style evolve, as it becomes easier to express the ideas that you’d like to get across. Learning how to express a clear, succinct thought is not a natural skill. This is that “voice” you hear English majors talk about so much, although it’s worth noting that finding your voice in technical writing is a hell of a lot easier than finding your voice in fiction.
One parting note: avoid looking at your readership stats, even when your curiosity prods you. You should be writing for yourself, and if it helps, perhaps one hypothetical reader (who might well be you plus or minus 5 years). Any more than that and I’ve found that you try too hard pleasing everyone, pleasing no one in the process.