ocusd is an excellent way to maintain your concentration and perform better at work, it only works if you want it to. After all, you have to set it up and limit your own time in a way that makes sense. And, if you want to remove the restrictions, there are plenty of ways to do so.
StayFocusd is a pretty useful extension to install on your work computer or during exams. It will help you stay focused and get more work done.