Buy a hardware wallet. I have several Trezor and can recommend them. You could also try the Ledger but I have never used this so can't comment on it.
Trezor is not expensive (around $80 I think) and is simple to set up. You can also store the main coins on it including all ethereum tokens.
It is also easy to use once coins are on it.
I don't suggest you use it if you are buying and selling coins daily as it will prob be too inconvinent but if you are not day trading it gives peace of mind that your investment is safe.