What was the hardest thing for you to understand when you first started learning about Bitcoin?

I’m trying to better understand what new people struggle with when they first start learning about Bitcoin.

If there is something you learned recently that you wish you had understood right away, what was it? Wallets, private keys, mining, the 21 million supply, or something else?

If people are struggling with certain ideas, maybe we can help fix that together and make the learning process easier for the next wave of newcomers.