When you already profit, it's already a good sign to sell your bag. Don't hold it for too long, there are consequences to it like the price could be dumped by users who hold more coins than you. If you are holding a reputable project though, you have the option to just keep holding until you need money for an emergency. I normally do that later option because I can just think of it like its just there on the wallet while I'm also busy with my dayjob.
It's mostly adviced to know when greed is in test, I think if enough profit has been made it will be better to take profit Buh most times we take profit too early on most potential projects which turns out to be a blast, so I think if the coin is being invested is worth the wait it did be better to hold for long, follow up on updates to see if they did be a launch of something which could eventually contribute to the pumps of the coin, if no much hype or good updates it will be better to just sell while in profit.