Margen
Without you paying it any attention, your heart does one of the most relentless jobs in the body: it pumps blood around a hundred thousand times a day. Multiply that by the years and you get billions of beats in a whole lifetime.
With each beat it pushes about seventy millilitres of blood. It sounds like little, but over a single day that's thousands of litres moved by a muscle the size of your fist. No factory-built pump could survive that pace for decades without stopping for repairs.
And it doesn't rest like you do. When you sleep, it slows down, but it never switches off. Between one beat and the next there's a tiny pause, and in those micro-rests added together lies its whole secret for not burning out.
Think about it: the longest applause of your life is the one your own chest keeps giving, without ever missing a beat.