I've once heard a quote that said - Success is gradual progress towards a worthy ideal, or goal. In World of Warcraft, when you level you character, you leveling is that measured gradual progress to a goal. The goal can be the next level, level 58 to go hit Outland, or even level 70. Either way with every quest and every Mob you are progressing. Once you hit level 70, that stops, at least for now. So what measures your success now?