Op, there's probably no need to panic, but it largely depends on other things you've done, and on what specifically is of concern to you. If you submitted KYC once, and you're not a serious criminal, your data probably won't ever come up anywhere again. Sometimes there are hacks and some data is leaked, but the odds of this happening to you are very low. If you don't want to submit KYC in the future, choose relevant services. If you want to now try hiding your identity via mixers, I wouldn't recommend it because mixers are largely considered illegal, and using a mixer might attract more attention than doing nothing. Also, if you don't pass KYC but use a debit/credit card to buy/sell cryptos for fiat, you're also identified because all bank accounts are tied to ID, so if needed, this way the authorities can get back to you. But since there are tons of people using cryptos all the time, they won't unless they have a very special interest specifically in you because you're a big criminal. So keep calm.