We are what we repeatedly do
I wholeheartedly agree with Doransky's latest post, and with Aristotle:
We are what we repeatedly do. Excellence, then, is not an act, but a habit.
One example that instantly comes to my mind is high school and maths. Planning to take an entrance exam we were put in a special group taught by one of the most notoriously strict teachers in the school. With one exception none of us were really special though, not what you'd call a natural born talent.
Classes were spent working from start to finish, no idling was allowed, and we were usually given a tremendous amount of homework. Often we devoted breaks between classes to discussing the solutions or what might come up next. And somehow by our senior year we became quite good. I can't speak for the others but never since then have I felt so confident in my maths knowledge.
It was slow and almost imperceptible, too. I only noticed the effect when my then-girlfriend was doing her homework with me looking over her shoulder: she was at a loss how to solve something really simple whereas I was nonplussed how she couldn't. After all, I knew, I wasn't supposed to be better than her.
Similarly every article or guide about writing starts the same: it's not all about talent, and even talent cannot achieve much without defiant diligence. If you want to be good (or get better at it) write every day, no exception.
This is one of the reasons I can come up with when asked why I still bother writing here: even if it was only me (or no-one) reading, it's still practice. And in the process, slowly, silently, I may improve.