Followup to: The Most Important Thing You Learned
What's the most frequently useful thing you've learned on OB - not the most memorable or most valuable, but the thing you use most often? What influences your behavior, factors in more than one decision? Please give a concrete example if you can. This isn't limited to archetypally "mundane" activities: if your daily life involves difficult research or arguing with philosophers, go ahead and describe that too.
Most frequently useful - that my interest in being unbiased can become a sort of bias of its own, when I hear arguments from others, I can easily spot the biases, and I've worked hard to recognize that I have built-in biases as well that I can't discount.