EE - What not to do!
Math EE - Things to keep in mind!
I recommend Pomodoro cycles: Please find here an awesome pomodoro timer!
Don't forget to remain focused during the long periods, and take a true break during the break periods. This works best if you have something to look forward to during you break time, it can be a video, ice cream, laying down in bed, quick meditation, a tasty snack, a walk around the house, a quick video game, anything you want!