In the movie Inception, we know it's not posible to know what was Cobb's totem (by this question). However, we know that he planted in Mal's mind the idea that the Limbo was not real, and that's why they commited suicide and returned to "real life".
How did he remember that Limbo wasn't real? Shouldn't he have suffered the same effects that distored Mal's mind? Is this ever explained in the movie?