I always lose focus if I'm only playing poker on a low number of tables, normally I browse some forums and listen to music/watch videos. Of course I'm using a HUD so I don't have to focus on picking up information on my opponents, making life all the easier when I have concentration lapses. Doing something like I do to pass the time might be harder if you don't use a HUD, or if you are playing 6-max. If that is the case and you find it hard to multi-task then I just play for as long a period as you are comfortable with and then take a break for a while. And then do it all over again, Yay!