The simplest durable lesson here is this: a journal is useful because memory edits your process faster than you think. Core idea: Without written priors, it becomes too easy to remember your thesis as cleaner and more disciplined than it really was. Why it matters: Journaling gives you a record of the reasoning, not just the result. In real life: Even two sentences about the setup, the risk and the invalidation level can expose repeat mistakes later. Common slip: The mistake is waiting until the outcome is known to write the story of why you acted. Try this: Explain in one sentence what problem this idea solves and what problem it does not solve. The point is not to memorize the label. The point is to know what variable is actually doing the work.