The Fatigue System was a feature in Final Fantasy XIV which slowly reduced EXP and skill points for players after a certain time limit. A controversial topic since the game's release, the fatigue system was finally removed as of patch 1.18. This system was in place to prevent excessive leveling, and was a penalty to gained experience and skill points. Upon gaining a certain amount of skill points on a specific class, the player might have start gaining "surplus" points on that class, that would not count towards the total.
The reduction was gradual and began at 10% reduced points, but could supposedly reach a point where the player would completely stop gaining skill points should they keep leveling, although there was no known case of a player reaching that point. The skill point gain message and the color of the player's current skill/experience points changed when in fatigue.
Fatigue was completely reset every week after the first skill point gain of that class after last fatigue reset (if you changed your class to a gladiator and got your first skill point on a Monday, your fatigue would be reset next Monday, even if you didn't reach surplus). Also, fatigue slowly reduced should the player start leveling another class, or simply stopped playing, encouraging the player to level multiple classes.