9. What’s one thing we must not think twice about spending?

This is obvious, but my answer is “books”.

A few years ago, I acted like a cheapskate when it came to books.

I remember picking up Antifragile by Nassim Taleb in a bookstore once. I decided I couldn’t spend 10 bucks on that book. I probably went to a Starbucks after that to drop $5 on a fancy drink.