I think that a lot depends on what exactly you are holding. The reasoning for each coin is very different. I would not sell the Ethereum or Bitcoin now. Because this time the price of more altcoin are going down. This happen because of bad news that featuring on line and other TV network. But in my opinion it will recover again in the next days or next months. So it is better to hold and wait for the right time. When the price of altcoin are getting higher and it can reach the price that you are expected for. So it is the time to sell your bitcoin.