When people die or otherwise fail to something (boss mechanics, ganking, whatever) while I don't because I saw it coming a mile away.
PVP on the Timeless Isle is a great example. I go there on my scrubbo alts (on a busy PVP server) and have no problems finishing my quests/rep farming/etc typically without dieing once.
Or another good example (not to beat a dead horse, as it were) is the green fire quest. I knocked that out in less than ten attempts, most of which were spent getting macros to work, with pretty subpar gear. The whole thing has pretty strict ability timers, everything happens in an exact order, and the major abilities are telegraphed blatantly meaning if you just remember the order and have the next counter-ability ready all you gotta do is halfass your way through your DPS rotation and you win.
Situational awareness... forethought... intuition... all lost concepts on so much of the population.