When I hit my "page 49," I took a little break, worked on a couple other projects, then came back after a bit. I read what I had written up to that point, and then picked the thread of the story back up. Ran with it for a ways, wasn't pleased with what I got. So I backed up, and tried again, doing a few things differently along the way. Still wasn't satisfied... I must have rewritten the two key scenes half a dozen times apiece before I got something that was almost decent.
I felt a bit like a sculptor working with dynamite. But when the smoke finally cleared, I had found what I needed amidst the various failed attempts: A bit here, a bit there that caught the spark of the storyline, or was precisely what I wanted a given character to say.
So, don't be afraid to keep writing. Or rewriting.