There may be many of you who write like Stephen King, who have a general idea where you are going with your novel but have decided to "wing it" every day during the NaNoWriMo, relying on your instincts to get you through this massive project. If you are able to do this, and be consistent with it, my writer's cap is off in your honor.
However, if you are like most writers you need a plan. If you have not discovered a method to "winging it" every day, then you need a dedicated outline. I usually start by writing down ideas on a yellow legal pad, mapping out character interaction, planning out the novel by at least giving it a skeleton. If you have not outlined before starting NaNoWriMo it will be ten times more difficult to write the novel this month than if you did.
If you did not take the time to write an outline before beginning this project and are finding yourself bogging down and getting writer's block (which I have stated before does not exist) then it would be worth some precious time to sit down and create one.
If you have created an outline, have a definite daily plan for what you will write, then why are you reading this? Get back to work!
Oh. And if you think you have to quit, remember what Harlan Ellison said: "Anybody can become a writer, but it takes a special person to stay a writer."