Use the pomodoro technique. You focus for a finite amount of time then take a break. You can work up from 20-min sprints to 50-min sprints. It's healthier for y

Use the pomodoro technique. You focus for a finite amount of time then take a break. You can work up from 20-min sprints to 50-min sprints. It's healthier for your eyes, body and mind to take a break at least once per hour anyway. When you break between sprints, make sure you're getting up and walking around - not just surfing Facebook. Get some water. Stretch. Do a few jumping jacks. Go to the kitchen and spend 5 minutes talking to whoever else is taking a break at the same time. Look out the window at the furthest thing you can see, to let your eyes relax. Eat your lunch outside the office. Grab a sandwich and take a walk or sit in a nearby park. The point is to get your brain some variety. Make sure you're getting enough exercise outside work. Be it jogging every morning, cycling to work, visiting the gym at lunch, pickup soccer in the afternoons, a softball league... And finally, consider a sit-stand desk. Something as simple as changing posture can go a long way toward reducing physical and mental fatigue.