I discovered a system of self-discipline that has worked for me every day for the past three months.
Noticing how important it has become for me to play a Sudoku game each day, I realized that the game includes a calendar where I get a star for each day I play. Over time, I have become reluctant to miss a day, and if I do, I end up playing two games the next day to make up for the missing one. This way, the calendar becomes filled with stars. That is my only reward, yet very compelling. The game takes 5 or 10 minutes, and it varies in difficulty. I justify playing because it improves my brain skills.
And so I decided to try to use the same system for my writing.
I now have a wall calendar, and every day that I write, even if it is only for 5 minutes, I give myself a star for that day. At the end of a week, I get a small reward - for example coffee out and a desert, and at the end of a month full of stars a bigger one, perhaps a lunch out.
What I found is that I am now 'addicted' to getting those stars. They are very visible on the calendar, that I pass by all the time, and I would not want to miss a day and see a blank spot. If, for some reason, I do miss a day, I make it up with two separate sessions the next day.
So, after three months of successfully following this system, I hope to continue, while my next book grows a page or two at a time