?Despite being warned of ice floes the Titanic maintained its top speed because making a fast Atlantic crossing was required to  live up to all the hype surrounding its maiden voyage. When the lookout spotted the iceberg there was insufficient time to avoid it. It's not just a case of being vigilant. It is also about resisting pressure to press ahead regardless of the risks identified. 

Chief executives have to be vigilant, to sleep with one eye open, to ensure nothing catches them or the organisation off guard. Whatever their level within the organisations managers don't like surprises. That's why they say if there is a problem let me know -  don't wait until it's a crisis. It's the same for chief executives times 100.  Of course you can't anticipate every problem. But you can require managers to let you know in time for you to take action to avert disaster or at least limit the damage.