i think ist better to sell the altcoin than to hold. because we don't know what happens next in the market maybe it goes up and down again. but if you hold the altcoin there is a possibilities to increase the price or decrease.
indeed many altcoins are down, often unsteady and unstable. If you want to sell it, you are free to determine which option is the best for him. but in my opinion you have to survive and wait for prices to be truly stable so you can make big profits. most likely the price will rise even though little by little and the key you have to wait patiently.