Making up your own deadline works until you realize that you know the deadline setter and can manipulate him or her.
I find working with writing partners provides accountability. The nicer they are, the less likely you’ll want to run on fumes and send them something that’s not quite ready or to your agreed page count. And my critique partners are very nice.
Don’t put the brakes on your writing. Finding a critique group through SCBWI or another writers’ group could be the fuel you need to maintain a steady speed.
Try it, and see if it works for you!