The forces of Shadow target the Keep of Fal Dara, leaving destruction and death in their wake. In the aftermath, Ingtar reveals that Darkfriends are amongst the denizens of Lord Agelmar's fortress. Secure in belief that the victory at Tarwin's Gap was decisive, and that every Shienaran in Fal Dara dedicated to the fight against the Shadow, that, even though guards were posted, the threat was always believed to be from outside. Loyalty to lord and land was never questioned, and they paid a price for it. It's a challenging situation: assuming the worst of everyone spreads distrust. Assuming invincibility opens the door to complacency and vulnerability.
Another danger confronts us, and [Verin] sounds as if it is a puzzle in a book. Light, the Browns truly are not aware of the world at all.
Moiraine, The Great Hunt, p. 87
"And of course," Verin said calmly, "the man who channels must be one of the three young men traveling with you, Moiraine."
Moiraine started in shock. Not aware of the world? I am a fool. Before she realized what she was doing, she had reached out to the pulsating glow she always felt there waiting, to the True Source.
Verin and Moirane, The Great Hunt, p. 92
Moiraine and Siuan were confident to the point of arrogance that their plans remained shrouded in secrecy. Part of Moiraine's lack of communication, I'm sure, was to continue covering tracks as to her true aims. Wrapped up in their own plans and causes, they neglect the fundamental realization that there are a multitude of solutions to a problem.
An effective counter to this is humility. Constantly assessing yourself against your biases; being attentive and considering all options, especially those provided from other team members. It takes a great deal of self-awareness to be successful, but, like most things, it becomes more habitual with practice. Pausing to ask 'why' can be effective: 'Why am I discarding this option? Is it because it is truly ineffective? Or is it for some other less relevant reason?"