Training Logs and Investment Journals Work Alike

Trevor L Taylor, a former Division I athlete who went on to train in road cycling and competitive weightlifting, built his investing on quantitative models, and the training log and the investment journal are the same tool aimed at two kinds of effort. Endurance athletes and lifters learn early that the record of a session matters as much as the session. An investor who keeps a dated journal of decisions is doing the same work: capturing intention, conditions and result while memory is still honest.

One structure for two records

A useful log, in sport or in markets, holds five things. There is the plan, written before anything happens. There are the conditions under which the work was done. There is the result. There is a grade that separates how well the work was executed from how it turned out. And there is a short note on what to change. The fields differ in detail, but the shape does not.

Research on everyday work supports the habit of writing things down at the end of each day. Teresa Amabile and Steven Kramer analyzed the diaries of knowledge workers for Harvard Business Review¹ and built their advice to managers around one idea: help people see their own progress. A larger body of experiments points the same way. A meta analysis in Psychological Bulletin found that interventions that increased progress monitoring helped people reach their goals², and that the effect was larger when the information was physically recorded or reported to others.

Writing the entry before the result

The most valuable training entries are made before the session: the plan, the target and how the athlete feels walking in. Only then does the record afterward mean anything, because intention can be compared with outcome.

Investment journals work the same way. The thesis, the expected range of outcomes and the reasons to sell are written before buying. Once a result arrives, memory tends to rewrite the original reasoning to match it. The writers at Farnam Street³ put the problem bluntly: people cannot trust their own memories of what they were thinking, and a decision journal works as quality control for thought, much as an inspection step does on a factory line. A forecast, a thesis or a game plan can only be scored if it was written down first.

Recording the dull variables

Athletes discover that sleep, food, stress and travel explain more about a given day than any single workout. Coaches also need a common unit for very different sessions. Carl Foster and colleagues showed that a simple session rating of perceived exertion⁴, tracked heart rate based measures closely across steady riding, intervals and basketball practice. One number per session, logged faithfully, becomes a usable history.

That history has practical stakes. Tim Gabbett argued in the British Journal of Sports Medicine that rapid increases in training load are likely responsible for many soft tissue injuries⁵, so load has to be measured over weeks and months, comparing recent work with the longer run average. No athlete can spot a spike they never wrote down. In investing, the dull variables are state of mind, time of day, what was read just before and whether the decision was rushed. Decisions made tired or hurried tend to share features that only a record reveals.

Grading process apart from outcome

A cyclist can ride well and finish poorly because of a flat tire. A lifter can make a lift with untidy technique and get away with it. Good logs grade execution separately from results, and the reason is a well documented bias. In five studies, Jonathan Baron and John Hershey found that people rated the same decision as better reasoned, and the person who made it as more competent, when the outcome happened to be favorable⁶. Subjects did this even though they agreed outcomes should play no part in the rating.

An investment journal answers with two lines per decision. Was the reasoning sound given what could be known at the time? What happened? The goal is to improve the first line, because the second contains too much luck to learn from alone. Writing for an audience can distort both lines. Jennifer Lerner and Philip Tetlock’s review of accountability research⁷ found that being answerable to others can reduce some biases, leave others unchanged and amplify still others, depending on the conditions. A log kept for a private reader avoids the temptation to look disciplined.

Reviewing on a schedule and changing the plan

Logs that are never reread are diaries. Athletes review weekly and at the end of each training block, looking for trends rather than single sessions, which is the rhythm that periodization builds into a season. A monthly or quarterly review of an investment journal does the same work. Which kinds of decisions consistently worked? Which reasons for buying proved weak? Where did a position stay too long or leave too early?

The final habit is the hardest. A log matters only if it changes behavior. If the record shows that heavy training on short sleep precedes injuries, the plan has to change even for an athlete who loves heavy training. If the journal shows that the best decisions come from slow research and the worst from fast reactions, the process has to change, even when fast reactions feel exciting. Data that never alters a decision is decoration, a point that ties this habit to position sizing and to the wider discipline of systematic investing.

What to leave out

A log can fail by recording too little, and it can also fail by recording too much. Athletes who track every available metric often stop reading their own logs because the important signals drown. For training, a workable entry is the plan, the work done, one effort score, sleep and a line of notes. For investing, it is the thesis, the position size, the exit conditions, the circumstances of the decision and a line of notes. Anything else should earn its place by proving useful in reviews.

Two composed entries, written for illustration rather than copied from a real log, show the shape. A training entry: five threshold intervals planned, six hours of sleep, legs heavy, four completed and the fifth abandoned, execution good early and fading late, short sleep for the third time this month. A decision entry: a small position in a stabilized rental asset, a five year hold, a sale if occupancy falls below the planned level, decided the same day it was first seen, and two of the last three rushed decisions underperformed. Neither is impressive to read. Both carry intention, conditions, result, an honest grade and one lesson, and either is worth more than a confident memory of how the decision felt.