So I was curious to know what you think is the hardest part about writing. This is obviously strictly an opinion for you and you alone, so there is no right or wrong answer. We all have strengths and weaknesses as well as likes and dislikes, so in responding it goes without saying to please be respectful, but I think it would be interesting to see what each author finds the hardest part about writing.
For me, the hardest part about writing is stopping. Because as the writer of the story there is so much going on in my head that I think things are necessary when they sometimes aren't. As we all know though, it's easier to add something than it is to take it away. So finding that balance of giving enough story to keep things going, but saving something for later, can be difficult to say the least.
For example, my second book that I'm currently writing is around 330k words at the moment. Granted, I am just about done with it so it won't go much more than that, but by comparison, Harry Potter and the Order of the Phoenix has only 257k words. So knowing when to stop is the hardest part of everything.