Playing in the market can be a little bit tricky if you had just arrived there. There are thousands of advice on how to handle falling curve market situations but the best advice would be your own instinct. Falling crypto offers a great opportunity for the investors to get a coin at a lower price in a specific moment and to hold it or sell it later. I am personally holding my coins and I ain't even buying right now because I ain't so trustful in this phase that market is for the last 4 weeks.
If you have a nice portfolio of altcoins try to be patient but if you are doubting your current portfolio exchange some of your cryptos to FIAT for safe keeping.