we say "HOLD" so you don't miss the train if the bitcoin price soars. Many people say that "when is the right time to sell bitcoin?" to be honest, the right time to sell bitcoins depends on the person himself. it all depends on your needs. this is the same as "when should we use the savings we have?" everyone will have a different answer. what is meant in this case is "hold until the price is high" or "don't rush to sell it".
however, very many people regret selling their bitcoins quickly just because they saw the bitcoin price go up high enough. however, if you feel that it's a fair price to exchange your assets for, no one will stop that.