A simple 'decision journal' habit that reveals your real blind spots

The method is to write a short entry every time you make a decision of real consequence: what you decided, why, what you expected to happen, what you were worried about, and what would tell you that you were wrong. It takes about five minutes and all entries go into one project. The key step, which most people skip, is going back every couple of months to pull up the previous quarter's decisions and compare what was expected against what actually happened.

Doing this revealed a consistent tendency to be overconfident about timelines, now corrected for automatically. It also showed that the things worried about were rarely what actually went wrong, and the real problems were almost never on the original worry list. Another pattern uncovered was systematically underestimating how long it takes to get other people to agree to something.

Normally nobody gets this kind of feedback in a career, because outcomes happen and memory quietly rewrites the past to make it seem like you always knew. Writing down what you actually thought at the time prevents that rewriting.