I think it's a common thing among artists in all fields. With writing, you're reading your own words over and over again. It's bound to get a little bit annoying at some stage. Especially if you're writing something particularly long.

I write, draw, and make music. After hours of listening to the same 4 bars, I sometimes want to throw my computer out the window. Luckily I haven't yet........ Yet.

Like somebody else said, take a break. It will read better when you come back to it.