When you've been using a computer to type up your manuscript for weeks, months or years, you can get desensitised to the power. You can make it look all pretty and professional, double spacing, page number, novel name and surname at the top right, 1-inch margins. Or maybe you feel like you can write better if what you have in front of you looks like a book. You change the page size and narrow the line-spacing to back to one. You add an italicised title to the top of the page and page numbers to the bottom, change the centring to "justified", format the chapter headings and add acknowledgements, a map, a quote, a copyright page, a title page and a contents page to the front, and an author bio at the back.
I've done most of these things.
But generally I stick to the manuscript style, which I'm sure will come in handy when it comes time for me to enter revisions.
However, all this computerness can become a bit much. There's a little too much power in the works, and you don't get slapped for going back and changing something – and you should get slapped, especially if it means you're working on a single sentence for more than two minutes.
I strongly feel that writing and editing should be kept separate. When you're writing, you should get into a flow and let the scene unfold at your fingertips. Stopping to edit each sentence will stop this flow. Now, this probably isn't a problem for everyone, but if you're a pedant like me, and want to get the sentence just right before moving on – then you need help. I'm going to refer you to Dr. Wicked. For more on his program, see my post here.
Enter the notepad.
The point of this nifty little thing is to get you away from all that unnecessary power. With great power comes great responsibility. I know I'm not responsible enough to stop myself from going back to edit sentences and paragraphs when I should be getting into the flow. That's not so easy when you can't just backspace and write it again. It actually takes physical effort to cross something out, and that means when you do go back and edit something on your notepad, you probably actually need to. And of course, the point here isn't to be neat and prettyful. You want to get into a flow, and you can help yourself to do that by taking out a notepad and getting rid of those obstacles and the resposibility that comes with power. Save the colours for when you type out what you wrote.
Also, notepads make you feel all writerly!