For me, the best thing about writing is the escape to other worlds that occurs when I write. It's like reading for me. I'm totally in that moment, in the scene, seeing it play out in my head as I write it.
The second best thing about being a writer is seeing your words and worlds being read and experienced by others. There's a special joy every time you see that your story has been accepted for publication, especially when it's due to readers choice. That makes all the stress and aggravation, tears and sweat worth it.