Over-optimisation
Over-optimisation is tuning each part of a system so tightly to what is measured that the system loses the unmeasured things that made it work.
How it works
Efficiency behaves like an ideology: it does not weigh the unquantifiable against the quantifiable, it treats the unquantifiable as zero and clears it. A system fitted perfectly to the past has no capacity to adapt when the terrain changes and no exposure to luck, because there is no upside left in it. In a fat-tailed world you cannot improve a group by improving the efficiency of each individual in it; to optimise the whole you have to leave slack in the parts. The talks name the effect and give no threshold for where tuning turns into damage.
What it changes for a personal brand
Look at the number you check most often and ask what it had to ignore to become a number. Then give one thing that has no number a place in the week that the metric is not allowed to take.