1. Remember the first draft ALWAYS stinks. This is where you find your voice, figure out the plot, and sometimes the story takes over and goes in a different direction than you thought. The first draft is messy and I know I personally will never show my first draft of anything to anyone. Get your ideas down or you will loose them and trust me that is not fun. Get it out of your head that it has to be perfect on the first go then when it is all done on paper go back and edit it. James Michener sold 75 million copies of his novels world wide. He said "I am not a very good writer, but I am an excellent rewriter."
2. Use a pen: Still having trouble just writing? There are several things that can help you overcome that. Try hand writing your work in pen for a while. I know I am so old fashioned but it really helps. Once you get in to the grove of not being able to erase words or sentences it will be easier on the computer. Develop the habit of just writing with out stopping. A good exercise for this is called Jam Writing. First you set the clock for however long you think you can write without stopping. Then as soon as your pen hits the paper just write whatever comes to mind. Don't pause, don't look back, don't think. Just write. You don't have to stop when the timer does but after time expires if you choose to continue the rules are the same.
3. Write or Die: Still can't control the backspaces? Still can figure out how to not stop? The other day I found this great app called Write or Die. They have a several apps for different devices (PC, Ipad, etc.) The primes behind this app is if you stop writing for a cretin period of time you are punished, that is you grace period. You can change how long the grace period is and you can also change the punishment. There are two that motivate me. The evil sound. If your grace period expire it admits a continuous annoying/evil sound until you start writing again. And what is more motivating that having your work deleted. If your grace period expires you have the option of setting it so that it starts deleting you work word by word. Now if you buy if for the desktop (it is only $10 and worth every penny) then you can also turn off the backspace. Talk about turning off your internal editor. Here is the link.
4. Practice makes perfect. The more you practice writing the better you get at it. A football player doesn't start out as a professional, he has to work and work in order to get into the big leagues. Even those incredibly talented players work to keep their talent sharp and improve. Carry a notebook with you everywhere and carve out some time everyday to write.
Hope that this is helpful for those of you writers who can't turn off their internal editor.