I once had a Sensei—the kind of guy you would never, ever want to upset in any way because I'm pretty sure he could kill you with his stare if irritation—who would spit out the greatest pearls of wisdom. Like a one-line-wonder with Kempo advice. One of my favorites is still:
Practice makes permanent.
Growing up I heard practice makes perfect. I suppose perfect practice makes perfect, but either way, the practice makes permanent.
For Kempo it is 100% true. Our dojo has been through a rather large handful of instructors, and each one has their own style of teaching. Not only that, each of them does something as simple as a kick with slightly different nuances. Which, can I just say, makes perfect practice practically impossible.
And I swear, every single time I put a great deal of effort into learning or perfecting a technique (see, there's that perfect word again) I end up practicing it wrong in some way. My instructor will correct me, and then it will take months for me to remember to do it the right way.
Unfortunately, not practicing is not an option. So the vicious cycle continues and I always have something new to learn.
The same thing happens in writing. Read something your wrote last year, and you'll find that you've got pet sayings, the same gestures and probably a really annoying sentence structure every time your main character walks into a room. (Or something, right?) You've written it dozens if not hundreds of times. Breaking those dang habits is so annoying! But also important.
So don't stop practicing, but listen to your writing group, read a book on writing, find a bad habit you have and fix it. And don't freak out when you find yet another issue you need to work on. Life would be boring if we all did it right the first time. Where would the funny stories come from?