So in a rapidly changing, novel situation never experienced before we should be held to the faulty reasoning of the past rather than adapting and changing plans

So in a rapidly changing, novel situation never experienced before we should be held to the faulty reasoning of the past rather than adapting and changing plans to reach the best outcome? "I think the same thing today as two days ago. It doesn't matter that aliens landed on earth in the meantime. That won't change my mind about aliens not existing."