Index Card Explosion - Screenwriting is dangerous!

I was in the middle of organizing some scenes and needed a bit more light. So naturally I flipped the switch to turn on my desk lamp...  forgetting that it also controls the fan I have in that room.

WOOSH! 

I went from thinking somberly about the motivation on my character to frantically trying to catch his story as it spun around the room in a flurry.I turned off the fan and the little squares of white paper floated to the floor and settled, some face up, some face down... some on the desk, some on the chair, some stuck in the blinds...

I just stood there for a minute and looked at them, in the middle was a card that had landed standing up on it's edge in the carpet... it read "CRASH!" 

For a minute I thought about the crash scene and began to back track from that point as I picked up the cards and re-organized them.

THE LIGHT WENT ON! (NOT LITERALLY THIS TIME).

A great idea for that scene just HIT ME...  I think this happy accident was the catalyst for an idea that will totally upgrade the entire story.

I have now TACKED the index cards to the wall, they won't get away from me again, but is that really a good thing?

I will never finish this screenplay!

Do you ever feel like you will just never finish the script you are working on? I have been writing my current action sci-fi script for over a year. If I could devote an uninterupted week to it, I could just knock it out, but then there is the re-write and the re-write of the re-write, right?

I did finish the detailed treatment on a flight back from Japan instead of sleeping, but how often am I going to be trapped on an 8 hour flight with no internet access?

INTERNET IS THE DEVIL!

Although the internet has been a great help to my process; seeking facts, downloading screenplays, interacting with other writers, following scriptchat on twitter... it has also been my worst enemy.

Every time I get in the zone (you know that magical place, right?), an email pops up or my phone buzzes that someone commented on my facebook status and I am off to check it. One hour later, I realize I have been playing on the interwebs and haven't written a single line... YET AGAIN!!!

HELP ME!

How do I get out of this cycle? 

How do you do it?

What are some good tips on staying in the zone?

So mad at myself!!!