Go to Mass and watch football!!!
okay, just kidding…kind of. I heard a thing about this on Catholic Answers one day, and if I remember correctly, it was a matter of avoiding “regular” unnecessary work. In other words, if you went to the office five days a week, you should refrain from doing so on Sunday. Also, if there was something that needed to be done, and couldn’t wait, then that would be okay to do. I’m paraphrasing badly here, but that was the gist of it. Obviously, there are thing to take into account, like what you do for a living. If you are a trauma surgeon, it’s not really reasonable that you should expect all accidents, etc., to cease so that you can avoid working on Sunday.