I think you have to let what D Stanley wrote in his first sentence really settle in: it's a market order.
You may want to consider a stop-limit order, as Schwab explains:
An order that becomes a Limit Order once the security trades at the
designated Stop price. A Stop Limit Order does not guarantee an
To enter a Sell Stop Limit Order, you must enter a Stop price below
the current security price and a Limit price less than or equal to the
Stop price. If the security trades at or below the Stop price, the
Limit Order to sell the security you entered will be activated.
This type of order may not be executed if the price drops too quickly. You may want to fine tune the order to not sell in full lots.
To avoid being left holding on to an asset that drops so dramatically, it should be used in combination with a Trailing Stop order, where you set the Trailing Stop order below your Stop Limit order. The Trailing Stop will execute as a market order, so you still risk getting out to late, but you will have a much better shot than simply putting a in a stop order.
A Trailing Stop for a Sell order sets the stop price at a fixed amount
or percentage below the current Bid price. If the Bid price rises,
then the stop price will rise by the increased points/percent amount.
Conversely, if the Bid price falls, the stop price will remain the
If the next day the price is drastically different, it will still behave according to the current bid and ask price, and not a fixed dollar value.