Earlier quoted context omitted.
I definitely feel my attentiveness and focus dropped dramatically after computers were introduced into my work life. It's a shame that computers provide such a thin line between work and entertainment.
You can make that line thicker. You can create a new user on your computer specifically for work, with a restricted environment. You could use VMs or dualboot or something. Personally, I'm very happy that we have devices that are capable of doing so many things.
I think most solutions to the problem are far too complex and this shall suit my needs just fine.