Scrap the rest of it and begin at the end, making it the introductory paragraph of your next draft. Believe it or not, this method often works. Writing a rough draft often clears your head of rubbish, so that by the time your last paragraph rolls out, you're writing and thinking more clearly. 

To put it another way, rough writing is often a way of giving yourself permission to say what you mean. A last paragraph summons up will and energy, allowing your thoughts to crystallize, your ideas to grow suddenly decisive. 

If, on re-reading the rough draft, you find the ideas turgid, flabby, or non-existent, check the last paragraph to see if it has started to work better. If so, then summon up your courage, take out your scissors or your samurai sword, and carve out a new start.

   Using The Paper Topic
   Rough Magic
   Grocery Lists
   Up Against The Wall
   Paragraph Outline
   Building On Evidence
   Traditional Outlines
   Starting With Last Paragraph