[JesseK]

Put down the video games, get off the computer.

That's what it took for me in college. Once I did that I found it was not only ridiculously easy to focus and get a 3.85 GPA, I also had time for a pretty nice social life with enough energy left over for working and volunteering. It's not a matter of what you spend your time doing; rather it's more a matter of how much thought you put into something regardless of what you're doing at the moment. Video games tend to take all focus and if something you learned isn't committed to long-term memory already then it's easily forgotten and easy to care less about the associated easy "fringe" work that's required to get the good grade.