When reading, or doing a long time block. Say a reading session of 3 hours, from 9am. It is more motivating to think that at 12pm you will be done, that will feel good, you will be smarter, and on schedule. That is a lot more freeing and exciting than wrestling with the idea of 3 hours of work. And it forces you to stay on schedule, because otherwise that 12pm or 1pm deadline for that progress marker, will get delayed.
This also works for junk food. In the moment, you feel like junk food, but you feel shit the day afterwards. So instead, focus on the next day and work backwards, do you still want the junk food?
From @balupton and @ExplorerSumit