To be honest, I was surprised to see the topic you wrote. If that happens, it's certainly the biggest loss for you to sell at the current price. I think there is no other way except to hold it and wait for prices to rise again to reach $ 20K.
I don't understand why did the OP invested on that crazy high price since most of the investors knew that that will be the end of the line there. I don't even know that it will be reaching $20K since most of the investors sold their BTCs at $19K.
The best way to do there is to wait, is to be patient on what may happen in the near future. The price will continue to increase, I hope, but it do annually so just need to wait for it. It is a disappointing loss but that is fine since that will be your lesson, a lesson learned out of mistake that you have done. Investing on Bitcoin is not a mistake, it is just the time of your investment.