Use your time wisely, but make sure to take breaks! The Pomodoro Technique (also called the Tomato Timer Technique), allows you to put aside small chunks of time to do focused work, followed by a short break. Learn more about the technique here: http://en.wikipedia.org/wiki/Pomodoro_Technique
Everyone has those sites that they "only check a couple times a day", but these can add up to a lot of time without you realizing it. RescueTime makes it easy to see. Download RescueTime's desktop app, or browser extension (Firefox and Chrome), and receive detailed reports about your productivity.