I have no idea what happened with CNB during the course of your trade [i.e. whether you were in profit at any stage], but remember Matt's mantra that he often repeats in his newsletters:

"after an inital good move, take half off the table and move your stop up to the entry/breakeven price, thus guaranteeing profits" (or words to that effect)

Of course, whenever you keep a trade open overnight, there is no such thing as a 'guaranteed' stop loss. However, by locking in profit on half of one's position during the trading day, any alarming price movement overnight only affects the remaining half and by definition mitigates any losses.