Have a plan. Do not make it up as you go. A plan need not be perfect, it need not be a life sentence, let it just be your guide, a way of knowing what might be coming your way.
“No battle plan ever survives first contact with the enemy.” – Helmuth von Moltke
But that’s OK. It is the plan, or it was the plan. Don’t then blindly follow it because it was the plan. You might have new information now, things change, adjust your plan.
And, at least you knew there was a battle. At least you knew there was a meeting at 2pm. At least you knew you were going to be asked about the four items from the last meeting’s agenda.