smart cookies dont crumble

Smart cookies dont crumble is an idiom which is referring to intelligence and the very importance of it. By saying smart cookies dont crumble, this saying is trying to point out that if someone is intelligent and use their intelligent wisely, then they wont crumble or in other words, wont fall apart, get nervous or anxiety when things get tough or have a hard time with things but instead can use their smarts to figure things out in a more practical manner.