Principles are like seatbelts. Nobody thinks about them until the moment they matter most.

A principle is not for ordinary days. It is a decision made early for a day you cannot see coming, and the reason to fix it now is that the moment it matters will be the moment you are least able to think, with pressure on and nothing weighed. Deciding in calm conditions is the entire mechanism.

Take a situation you have been dreading and settle what you will do before it arrives. Write it as one sentence, and keep the sentence short. When the moment comes you will only have to remember it rather than invent it.