Composition and an increased use of references. I always find myself trying to draw something right from my imagination and end up realizing that my imagination is kinda shady and unclear.
I also tend to draw with pencil and subsequently abuse eraser a lot. To a point where you can still see the last couple pictures I attempted to draw on a sheet of paper. xD
My advice: don't do what I'm doing.
Gotta say, this is basically me as well. One of my main weaker aspects is not doing enough proper pre-planning. I would have ideas for drawings that I'm eager to jump into, but then realize I should have thought more about the overall layout and composition. This results in me having to make adjustments to my work later on, and as you mentioned, leads to lots of erasing. But when using a medium like pen or paint, it can be very difficult to remove/cover up original flaws, and it becomes time-consuming to go back and make changes to.
I would also say that I am kind of a perfectionist, where I would initially think a piece is finished, but then I constantly notice little details that I see as flaws. The worse part is that I keep looking back at the piece even after making adjustments, and I would notice another flaw, and
another, and
another...
One recent example of this is the Zamazenta image I made in my signature. After uploading it on an image-hosting site, I thought that it looked great and that I was completely done with it. But then I just kept looking at it, and then I noticed some uneven lines and curves, which bothered me. I decided to go back and make changes to them, and then re-upload the image. Yet, I did this repeatedly and spent more time than I had expected over the course of a few days and even a week or so later. Granted, I am not the most experienced in terms of digital drawing, so the issues of pixels standing out were something I had kept wondering about and experimenting with. This also has to do with my issue of lacking proper pre-planning, since I falsely believed that I had fully familiarized myself with this Pokémon's detailed shapes and design. Even now, it doesn't seem like I captured some details the most accurately and evenly, but well... I'm gonna let it go now! Lol