you can't fix stupid

It is often fruitless to help people that are stupid and do stupid things.

日本語の意味

愚かな人や愚かな行為は、いくら助けようとしても改善されないという意味。 / 愚かさは変えようがなく、無駄な試みになるという考えを示す表現。

I tried explaining the safety procedures three times, but as they say, you can't fix stupid.

安全手順を三回説明したが、よく言われるように、人の愚かさは直せない。

意味（1）

It is often fruitless to help people that are stupid and do stupid things.