Dark Fantasy isn't about being scary or about evil things. (I've heard people grumble about their silly misconceptions when I name my genre.) It's about studying human nature and how far a person will go to do what's right instead of what's easy under increasing hostile situations -- with lots of magical creatures/faeries/magical worlds/hidden worlds/magic in the mix.
Of course. There are different types of writer's block. Identify which type you have before jumping in.
The first has to do with the story: take a long walk, clear your mind and the solution to the story-issue will come to you.
The second has to do with exhaustion: are you sleeping enough? How is your stress-level? Are you taking care of yourself? A well-rested you will be much more effective.
The third is all about burnout: a good night's sleep won't help. This is the place where you have to stop. You need to refill your creative well by travelling, seeing new and wonderful things, relaxing and leaving the stressed-out you to become human again. Only then can you do your writing justice.
Instead of writing whatever I'm in the mood for, I now stick to a schedule to complete a story to get it published -- there is more accountability now.
Besides proper grammar and proofreading so readers won't trip over language issues and iffy facts? Depth: emotional for the characters, physical for the world of the story, personal for the reader.
I've been creating characters, worlds and adventures since I could talk. I've been writing since I learned how to hold a pencil. I decided to turn it into a career a couple of years ago, inspired by the idea of a story that has since grown. Some of this inspiration can be seen in "Once...".