Writers told me not to rewrite/revise/polish anything until you’ve finished the first draft. You’ll drive yourself crazy. They also advised not to read anything you wrote over. Personally, I always read my stuff over, because I love my characters too much. Usually when I’m halfway done, or wrote a lot, I print it out to read over shabbos.
If you’re getting bored, it’s not a bad idea to move on to another story. Some stories click more than others. I sometimes write 2 or 3 novels at one time because my head is filled with ideas. Or you can always think of twists and give your characters obstacles to overcome. Also, if you feel like your story is dragging and you want to get to a better scene, skip the scene you’re struggling with and move on. You can get back to it later. Lots of writers don’t write in order (I do, because I need order, but everyone writes the way they write. There are no rules–just grammar and stuff…).
Hope that helps. Good luck!