Isaac Newton could calculate the motion of the planets, but not the madness of men, and it cost him nearly everything he owned.

In seventeen twenty, Newton held shares in a London trading company whose stock had been climbing for months. He sold early, took a solid profit, and walked away satisfied.

Then the price kept rising without him. Friends who stayed in kept getting richer. The fear of missing out beat the mind that had already made the right call. Newton bought back in near the top, with a far bigger sum than before.

The stock collapsed soon after. Newton lost what would be worth millions today. He later said he could calculate the motion of the heavenly bodies, but not the madness of men.

Here is the actual lesson. A pattern that has stayed calm for a long time feels safe for exactly one reason: nothing has broken it yet. That feeling is not proof of safety. It is only the absence of proof of danger — and those two are not the same thing.

A farmer feeds a turkey every single day. The turkey's confidence grows with each calm day, right up until the one day it doesn't. Nothing in the turkey's own experience warned it, because every day before that one had pointed the other way.

A stock that's stayed quiet for months doesn't get safer with each quiet month. It just collects more untested trust.

Newton wasn't wrong to buy the stock the first time. He was wrong to let other people's rising profits talk him out of a decision he'd already made correctly.