Every life form has the urge to maintain themselves and worry about offspring.
We instinctively avoid danger.
zorg1Malodorous or spoiled food, brightly colored poisonous animals. Dangerous animals.
We protect ourselves from scorching sun and extreme cold.
We lick (literally) our wounds.
Knowledge of microbiology, and the relationship between bacteria, fungi and diseases helps us to see risks of what we cannot see with the naked eye anyway. With a thorough hygiene and higher life expectancy as a result.

Your most important tool to be self-sufficient is your own body. So keep it healthy, firm, smooth and in good condition. You need it every day.

The greatest threat to mankind are we.
Not necessarily as a killer of our species, but rather as misguided and profit-driven producers and consumers of substances and radiation of which we cannot estimate the effect (on long-term) in our environment.
And to which we cannot (anymore) protect us too.

Do not worry about your heart, it lasts your lifetime. (W. C. Fields)