After years of trying various methods, I broke this habit by pitting my impatience against my laziness. I decoupled the action and the neurological reward by setting up a simple 30-second delay I had to wait through, in which I couldn't do anything else, before any new page or chat client would load (and only allowed one to run at once). The urge to check all those sites magically vanished–and my 'productive' computer use was unaffected.