The one mantra in crypto world is hodl. You should have waited for a longer I wish. Right after ICO is completed and a coin is listed, its value decreases. After two months or three it starts increasing in values. It is my experience.
If the coin is legit and you think that it will hodl for the future than holding such coin for long time make sense. But if unsure or think it is only a temporary phenomenon than on listing or whenever the price is right for you sell it and move on.