The original statement isn't always true.  

True, profits or losses aren't realised until you sell, but holding and never selling doesn't guarantee not realising a loss either.  Ask anyone who has held stock (without selling) of any bankrupt company, or even plane tickets of an airline that has gone bankrupt.   Or even in crypto, anyone who HODL'ed any of hundreds of alt coins whose charts have ONLY gone straight down after a small initial climb to sub .000X since their inception.   There comes a point with some assets where you no longer have a choice of selling as the asset in question has already pancaked.   It's like saying you won't crash into the ground if you don't parachute out of the plane first.   

That said, this isn't FUD... I both HODL and trade, but do disagree with the original statement.