If the project isn't good and shouldn't have joined in the first place then sell it immediately but if it's quite good i recommend just hold it for awhile because most of the tokens just go lower and lower until it dies
Yes i agree that your decision should based on the project that were joining like if the project is quiet good and promising you can really hold it first because it has a big chance to rise even more and you could have a huge profit out of it. However if the the project is not that good then you can already sell it if you think its enough because it will just drop and drop and later it will have no value anymore.