Runs are a normal feature of any sequence of uncertain outcomes. Flip a fair coin two hundred times and runs of six or seven in a row are to be expected. A trading record with a positive expectancy and a modest win rate will therefore contain losing runs that feel like proof of failure.
The risk is behavioural. After a winning streak, confidence rises and size often follows, although the next trade is no more likely to win. After a losing streak, many traders either abandon a sound setup or press to recover. Both are reactions to a pattern that may be nothing more than chance.
Whether outcomes in real markets or sport depend on recent outcomes is a question researchers have argued about for decades. For a journal the practical point is simpler: you can test your own record. Compare your size and expectancy after two wins in a row with your baseline, and your behaviour after losses with the rest.
A written rule helps: the size of the next trade comes from the plan, whatever the last few results were.
Streaks also matter for tracking, in the good sense. Counting consecutive days on which you completed your review or kept your plan is a streak you control.