There's a podcast called the Nerdist Writers Series, which is a TV writers panel discussion about writing, with different writers week to week. I find it interesting to listen to, both for the writers' stories and to learn about TV writing. But I can't tell you how many of those people talk about how excruciatingly painful it is for them to write.
Reminds me of the old joke about the guy who goes to the doctor and says, "Doc, it hurts when I do this."
The doctor says, "Then don't do that."
Which is what I would say to people who find writing painful.
But, anyway, rewriting - God help me, I enjoy it. For a first draft, you chase all the rabbits down their little holes, looking for the ones that will best contribute to the story. Along the way you pick up characters who are interesting and fun (or crazy or dangerous or stupid) who ultimately end up being unnecessary to the story.
Don't get me wrong. It's really fun when you're humming along on the first draft. At times the story seems to write itself, the characters come up with all these really cool lines, and you wake up early just to get at that computer. First drafts can be a blast.
Right up until you hit a wall. How am I going to get from here to there? Or why didn't I realize this character was going to have to do this thing that he wouldn't really do? Of course, the next day when the answer pops into your head, it's back to fun and games.
The rewrite is when you jettison all the extra baggage and keep only the stuff that best moves the story forward.
You discover you can consolidate scenes, that two things could be done more effectively in half as many pages. You figure out ways to give readers clues to the resolution of the story - and just as important - you figure out ways to draw the reader's attention away from that clue you just fed them, and pay attention to something else that's not going to help them solve the mystery. You make your characters consistent. You solve plot problems. You fix the book, changing it from a big sprawling mess to a tightly-woven, suspenseful roller-coaster ride.
And that's fun.