Change your behavior by rewarding your hard work and punishing your slacking off.
Concrete ideas to modify and expand this hack go here.
I've had good results using the InvisibleClock (../BuildAnExoself?) for this hack. I used the Custom Timer feature with a 60-minute repeating timer. I set distinctive alarms for the 20-minutes-left mark and the 1-second-left mark. I worked the first 40 minutes of every hour, then (alarm 1) I did something fun for 20 minutes (technically, 19 minutes and 59 seconds), after which (alarm 2), I went back to work for another 40 minutes, and the cycle continued.
This kind of system is great for situations where you're billing for work. I call it the 2/3 system because for every three hours, you have two hours of billable work (and one hour of unstructured fun).
It's starting to seem as if this hack and the ../BuildAnExoself? hack are forming part of a larger framework. Certainly carrying the InvisibleClock rather than the MotivAider has given me many more options for shaping my behavior in a Skinnerian way.
By the way, a friend recommended Skinner's autobiography to me as an extension of the kind of detail in the article "Skinner As Self-Manager".
For future reference (of me, mostly), here are the specific InvisibleClock settings:
It's struck me recently after reading this, aren't we reinventing the clock-tower. There used to be a tradition in towns for the clock tower to ring the hour/half-hour. People in the town used use it to effectively run their business. Lot's of modern towns are silent; time creeps by. Perhaps this is one of the unplaceable elements when people talk about the hearts of communities: collective time--- AndyGavin
The hack is really about rewards, punishment, and operant conditioning. The timer is only incidental. It's there so you can reward yourself with 20 minutes of fun after 40 minutes of work, or what have you. If you decided to reward yourself with a caramel after every chapter you read in a textbook, that would be the same basic technique, but without any timer at all.
Errata go here.