And then actually stick to it.
Its easier to stay focused if you only have 45 minutes of a task ahead of you (a report, study essay etc) rather than hours and hours.
You can easily justify ‘5 minutes on FaceBook’ or ’10 minutes checking email’ when you have an undetermined amount of time on a task, and we all know this leads to a slippery slope of procrastination.
During the designated time, strictly adhere to the plan and do not touch your phone, browser or any other distracting objects. When the time runs out, stop. That’s it.
The upper limit gives you the feeling that it won’t really last that long. If you need to do more, repeat this several times throughout the day.