Losing money on a bad idea is tuition. Just make sure you actually take notes in that class.

A failed attempt that cost you money is only worth whatever you extract from it. The money is gone either way; what varies is whether you end up with knowledge or just a smaller balance. Most people avoid looking closely because the examination is embarrassing, which turns an expensive lesson into an expensive nothing. The review is the part you already paid for.

Write down exactly what you assumed that turned out to be false. Not that it was stupid, but which specific belief was wrong. Keep the page and read it before the next thing you put money into.