I made a ton of financial mistakes in my life especially when i was younger. I find with getting older the awareness of certain risks grows and you learn to not make the same mistakes again.
One of my mistakes is trusting people to much with money. You can't almost trust anyone in this world with money even not your best friends. I once got scammed by a friend of mine for a very big sum of money, it was basically a confidence scam that he did. I sold a car and never got my money.
Another bad mistake that i made is leaving to much money on an exchange without 2 factor authentication turned on. Always use 2fa, hard lesson learned for me. Lost 10 000 dollar worth of ethereum when it was still worth 40 usd per ethereum. Could been a few 100k at the peak of the bubble end 2017 if i would not get hacked.