We all get lucky. Once in a while we do something really stupid that could have ended badly, but didn't. Recently I saw someone texting walk out into oncoming traffic, narrowly missing a car whose driver slammed on the brakes. As the shock fades, we realize we never want to be there again. We can make the most of second chances by building margins of safety into our lives.
A margin of safety is a cornerstone of engineering. Engineers design systems to handle far more emergencies, unexpected loads, misuse, or wear than anyone normally expects.
Take a bridge across a two-hundred-foot river. It might carry 50 to 60 cars at once — at least 240,000 pounds. That is the minimum. Only the worst engineer would stop there. What if people walk across, cars park on the shoulder, or 20 cement trucks roll on together? What if weather slowly weakens the materials? You never want the real load to come close to the limit. Otherwise one seagull lands on the railing and the whole thing collapses.
So you first imagine the maximum load the bridge should ever see, then design for at least double that. The gap between what a system is expected to withstand and what it actually could is the margin of safety. That is why we feel calm on bridges, in airplanes, or jumping on a bed upstairs. Extra strength has been built in. Accidents still happen, but these structures can take quite a bit of the unexpected.
The key is what you design for. A margin built only for the worst weather in recent memory is not the same as a margin built for the worst that could still happen. One coastal plant was strong enough for recent storms, yet not for a tsunami that was unlikely — but clearly possible — in a region with frequent earthquakes. It could have been built to handle more. It wasn't, because extra protection is expensive. You are safer, but it costs more.
When the stakes are low, that trade-off is easy to accept. Few people insure a cheap wedding ring. Preparing for the worst we have seen is not the same as preparing for the worst.
How do we bring this into ordinary life? We rarely see how close we have come until after the scare. Then we adapt, because luck is a poor plan. Margins of safety reduce how much we depend on chance.
You cannot put them everywhere, or life becomes all margin and no living. But you can ask what load your life is designed to carry, and how close you are to that limit. If your expenses equal 100 percent of your income, you have no flexibility. A job loss, a flood, or a serious illness would change the load your finances have to support. Without savings, the structure can collapse — including the roof over your head.
Spot the unlikely but possible risks, and leave enough room to keep going if they arrive. Then a missed paycheck is absorbed, instead of putting dinner at risk. To find where else you need a margin, think of the times you have been terrified and desperate. Those are good places to start learning from experience — and making the most of your second chances.