I am pretty good at focusing on the job at hand, most of the time. Unfortunately, though, I still have websites that I shouldn’t visit that I do visit (some of them way too often, and they are almost imprinted in the muscle memory).
In order to solve this issue I use on all my computers StayFocusd (on Chrome). It is an extension that allows you to block specific websites for a while (or even forever) and it syncs between multiple Chrome installs on different computers. I actually have some sites that I will be able to read in 13241. Soon…
The extension is pretty simple to use: you have a list of blocked sites, of allowed sites and you can use either to block all but the allowed ones, to allow all but the blocked ones or to block all :D I actually did this by mistake and I had to uninstall the extension, since Chrome considers the extension options as being another website – albeit local, not world wide web (this is the way Chrome is built).
If you have bad self-control with the websites that you read, I think StayFocusd is a good option for you to try.