If there's no way you can possibly withdraw all of your assets to some fiat currency like USD, then I suppose USDT would be an okay alternative; Tether's got a pretty rocky history and I don't like it personally, but it's held up so far and people still seem to trust in it. The coin also hasn't fluctuated too significantly from its target price of $1 to date yet (though it has on a few occasions), though there's no telling if it'll stay like this.

If you're already nervous about the markets, it's not a good idea to stack on even more risk for a reward that you might not even see.