Personally, I've never really stressed about the 13, and when you look at the stats on accidents or serious stuff, Friday the 13th doesn't exactly blow the numbers out of the water. It's exactly what everyone else says: our brains are super good at spotting patterns and remembering coincidences that fit our beliefs, while forgetting thousands of 13s where nothing weird happened. It's pure psychology, not physics or curses.
But there's one thing nobody's brought up yet: the superstition around 13 also reinforces itself through real material and social consequences. Like, there are buildings in the United States that straight-up skip the 13th floor, or airlines that don't number the 13th row. That means people act differently on that day because they believe it's cursed, which can create actual real problems. You've got someone who's more stressed, sleeping badly, making weird decisions because they're thinking about it too much, and boom, problems show up - but it's not magical, it's just the effect of your own anxiety.
So it's neither pure stupid superstition nor a real danger: it's more of a fascinating example of how our beliefs can actually change our behavior and therefore our reality, without anything supernatural involved.