if all the coins owned have decreased in price, then I agree that the best decision is to hold because if you sell it then you will only get a loss
but if you want to hold, you also have to think about it in detail, because it doesn't always hold to be the best decision.
The only problem about holding is you miss the other possibilities. Sometimes you end up making ton of money from holding but sometimes you just get stuck for months. That's why I don't think holding only one coin is a good thing.