The Systemic Explanation: In systemic navigation, particularly "dead reckoning," a vessel calculates its current position by using a previously determined position and advancing that position based upon known or estimated speeds, elapsed time, and course. Your emotions (anxiety, temporary peace, frustration) are environmental forces—they push against the hull like wind or current. If you steer by the weather, your vector will constantly shift, resulting in drift. A written log provides objective, fixed coordinates. It allows you to calculate exactly how far the "weather" has pushed you off course so you can recalibrate your trajectory back to true north.