Mistakes are learning experiences, or as I like to call them, experiments. If you reach the desired result then you add it to your bag of tools to use when needed, but it doesn't stop there. You might find a better tool to use down the line that makes an older one obsolete. This can be applied to writing like nearly everything else.
ReadingReading fiction from my favorite authors and others newer writers is probably the most important thing I can do to help improve my own writing. I wrote a whole blog post on critical reading where you can pull different things you learn from your reading experiences to apply to your own writing. I can't overstate how important the influence of other writers have on what you write, but when you apply it to your writing you must retain your voice. You are the best at being you.
Writing Advice BooksAdvice on the craft of writing is everywhere. There are many books written on the subject as well. These can help you with the general craft of your writing which can be a good thing, but it could also stiffen your words. Trying to fit your work within a strict template others have set out for you can dry out all of the personality of it. I have seen this time and again in film and TV. The story can be compelling and interesting, but with the personality of a block of wood.
ExperimentsIf you find something in a piece of fiction or writing craft advice that you want to use then try it out. Write something that uses it in your own voice. Not everything will fit in with your writing style. Writing styles are like fingerprints. If you try to meld a unique flavor it might make your soup not taste quite right. Not everything is going to work with what you are trying to do, and that is OK.
Keep what works and toss what doesn't. We are constantly evolving beasts and our writing is also. Constantly experimenting and trying different things can help you evolve and grow as an author. Now I have to see a man about a gamma radiation explosion. He told me not to make him angry.