Writing is lonely. Until that moment you write your first character and suddenly you have company.
Park your ego and listen to your readers. They can be your best friend or your worst enemy. But chances are you'll learn something from them.
Writing is easy. Writing a publishable book is hard.
If you aren't willing to put your best work out there, write for yourself. Don't ever publish.
People who say you can't do something should be ignored. They're probably talking to themselves.
I'd be lying if I said killing off characters wasn't therapeutic in some way.