Writing what you feel.
Oftentimes, we're told that you can't write certain things because it may not get read or they "might not" like it. So, we hold back on seeing our vision through and that takes away from the creativity that wants to seep within. It's hard when you hold the pen to your imagination but you're afraid of going against the grain and you end up fearing the worst, causing your novel that you envision to lack details the way you'd want it.
Being an author is hard but it's so much fun because for however long your book is, you're somewhere else, someone else, and doing things that only you could dream of. Every character from the main to the supporting is a vivid collection of your imagination and it's a damn beautiful thing.
The beautiful thing about our art is, mistakes are necessary. You're human, you're supposed to make them. You grow with each novel and you'll read over old material and feel your growth. And if you do it and you don't feel and see the change, take a step back to focus. You'll also challenge it when you create your next masterpiece, it's part of the process. As long as you know every novel won't be like the last, you'll be fine. There's going to be times where you can't shake the latest novel you wrote because of the high you get when you know "I felt the growth in me. I'm getting it right and it only gets better from here." Embrace that feeling because it's going to be there every time you create your next banger.
Never let what others go through persuade you that your writing isn't good enough. Once you put that pen to the pad and the ink on the screen, you're living your dream. Never doubt what you create. Enjoy the ride and pen the hell out of your next best seller, whether you publish it or not, it's an accomplishment, YOUR accomplishment. So, write your heart out.