Another phrase I usually read is "it takes time to develop". This makes their supporters hopeful even if the price and volume keeps dropping.
To be fair, I don't think this statement is being used that much with altcoins though, mostly just with bitcoin. Though bitcoin is never guaranteed to "go back up", if there's a coin in the cryptocurrency space that's most likely to go up, it's definitely bitcoin. But of course, as always, risk control.
Those who think that shitcoins will "always go back up" are simply delusional.
Ironically, many of these bag holders use the bitcoin comparison. They think the alts they are holding will also go up after a few years like what happened to bitcoin.