set yourself some limits. i set timers...i decide i'm going to spend 45 minutes on the computer, set a timer when it goes off i shut the computer down. when i'm sewing i set a timer, after 45 minutes of sewing it is time to get up and take a walk, get something to drink, stretch...or even move on to something else. then you can decide...later i will go back and spend another 45 minutes...
there are days when i spend lots more time here then i should, but some days i just dont feel like sewing or have trouble getting going on something. i still set the timer and make myself take breaks from it...
sometimes i think timers are my best friend!