I engage in periodic bouts of such swing trading. When I get caught holding a bag of stinky fiat, and no way to buy back in without a loss, I just stay in fiat. Options include:
- enter a limit buy at a strike price below your last sell and forget about it. It may execute in the future if the market dumps again (I have a ladder of open orders in the $1000 to $2500 range that may never execute)
That sounds like a plan, but I'm so impatient. As an INTP, sticking to a decision is not my strong suit.

- you'll need some fiat to pay the cap gains tax on your profits anyhoo - when april 15 rolls around, cancel your open orders if you need the dosh
No comment.

- pull your money and have a fling. If you tie a bank account to GDAX, withdrawals are free. Yes, free.
I don't want my bank to know that I am fiddling around with BTC. Not sure what their policy is, but don't want to take chances, and have them close my account. That is why I have lately been using the Paypal route. Then I can transfer from Paypal to my bank and all my bank sees is that I got money from Paypal.
And the number one answer:
- Buy some BCH. As $/BCH:$/BTC trends toward 1:1 you'll be back in profit.
Another example of my crappy trading skills. I was speculating that the Bitcoin Cash whales would want to keep BCH more profitable than BTC, so I ended up using some spare satoshi on Bittrex, Yobit and Cryptopia to but BCH near the ALT

Don't worry Btc maximalists, the amount I spent was way less than.1 BTC. Now, I am patiently waiting for BCH to get profitable enough where it makes sense to actually rent hash at MMR. I'm not going to buy BCH outright anymore. It's way more fun to pay a miner at MMR and accumulate (or mine and dump) that way.