All of them are the same, including Bitcoin, they just work the same way and once you have lost your private keys there are no ways to revive them back. Whenever you’ see those private keys they will always give you a warning to store them safely so you don’t lose them, because once you lose them they are gone for good and there is no way to recover them. So just forget about it. But if you’re still in possession of your Ether, you can still create a new private keys.