This is something I find as well. When I first got an editing computer at home (MacPro in the miniDV days) I had dial-up so would only check emails on a separate computer. Later when I got ADSL and could connect more than one computer I decided that it was too distracting and kept the edit computer offline and used the other one as the general computer, email, web browsing, etc. That was good for a few years. Then the laptop got too old to run some new things and I ended up making the MacPro the single computer for everything so it had to be online.
Big mistake, way more distractions. Say I'm in the middle of concentrating on a scene, there's all the subtle things you have to notice in the footage to make creative decisions that you have to muster up, then you get interrupted by an email coming in.
Another thing is when things get tough it's natural to avoid it but you have to force yourself to stick to it and figure it out. When distraction is easy you can avoid it easily. You can tell yourself that you're just taking a break but a real break would be not involving a computer (going for a walk, etc.)
I read about how David Lynch meditates every day and has for decades. This might be why he's so prolific.
(I also have a theory about the increased diagnoses of ADD in young people. Maybe they're just normal but living in a time when their environment is more distracting than previous generations and to manage.)