The 20-Second rule is a technique to make consistent progress on your goals.
The 20-Second rule is this. The harder it is to start something, the less likely you are to do the task. So if you want to live a productive life, you have to adjust your lifestyle and environment to make it easy to start working.
The example used in the video is that if you want to stop playing video games and want to start reading or practicing guitar, then you have to create an environment that makes starting those tasks easy and video games hard. So put the controllers away in a shelf, put the remote far away from the couch, put the book on the table right in front of the couch, put the guitar next to the couch and make sure its tuned properly and ready to play right when you pick it up.
I find this really interesting because many times I have been working in my room and then I see my bed and i just go back to sleep because its so easy. If instead of a bed I had a futon and turned it into a couch as soon as waking up, it would take more effort to go to sleep and I would probably keep working. Or if I left my room and worked in a separate place where there is no bed, then I wouldn't be tempted to go back to sleep.