I'm finding myself habitually Alt-tabbing to my browser whenever I finish something, no matter how trivial; whenever I run into a problem requiring more than five seconds' thought; and every five minutes, whatever. So far I seem to be able to catch myself and remember that, hey, that's not what I'm supposed to be doing. Unfortunately this particular day was consumed by administrivia, so I still wasn't actually productive; but at least I wasn't just surfing the web.