A common writing trick is to stop mid-sentence so you've got somewhere to start the next day. You can apply a similar logic to any task by leaving yourself a reminder in a text file that displays the next time you boot your computer.
Blogger Roger Barnes outlines how he uses this approach to make sure that tasks started late in the working day are completed first thing the next morning:
Create a text file on your desktop, and add a shortcut to it in your startup programs. By doing this, there is an easily accessible dumping ground for last-minute notes or reminders, and it will pop up in your preferred text editor the next time you log in.
If you do finish each day by shutting down and start each day resuming your PC (not the most power-efficient approach, but a reality in many workplaces), it's a fast and simple way to stay on track.