There was an interesting description of the useless kind of practice in Talent is Overrated. He describes a golfing session where he just hits the balls around, without any plan on what to work on. While this kind of practice can maintain a certain skill level, it is not a path for improvement.
I see the same thing with my essays. I’m just writing things, but I’m not really responding to any feedback I get. In fact, I fear my skills have regressed because I just rediscovered that I should be writing outlines.