I like so many things about being a writer, but I would have to say the best thing about being a writer is discovering the story.
For me, writing is very much like reading a book for the first time. The whole time I'm working on a manuscript I'm finding out things. I laugh when my characters make a joke and cry when they are sad. I'll even think things like, "Oh! I had no idea! That's awesome!" When the story takes a sudden unexpected turn.
The journey is the best part of just about anything. Writing is no exception. Enjoy the journey!