Murphy’s law is a popular adage that states that everything that can go wrong, will go wrong.
It’s important to minimize risk, but even the lowest-risk options are susceptible to failure.
When things go according to plan, celebrate.
When things don’t go according to plan, learn.
Don’t fall into the trap of despair; remember: even the safest options sometimes fail.
In he basically argues that you can never predict when such unpredictable events can happen. It's better to figure out what type of downsides you're vulnerable and prepare for that.