I'd argue keeping funds on an exchange is the most costly mistake in aggregate. people treat CEXs like banks, but they're not when one goes down (FTX, etc) everyone loses
the first security habit should be self-custody, get a reputable hardware wallet or open source mobile wallet, and move your coins off the exchange as soon as you're not actively trading.
The reason why a lot of people prefer to turn to using CEXs is because it’s very convenient, but regardless of that, they’re not like banks and they sure don’t offer the same kind of protections that banks offers. Whenever something goes wrong with your money inside an CEX, there’s no place you can walk to complain, especially when you’re limited by geographical location, all you can do is rely on their customer support system, which sometimes isn’t entirely reliable and can take like forever to fix whatever issues you’re having.