Before investing in crypto currency, you should be prepared to lose some money, then you're mentally stable to continue with the game of crypto currency.
Thats true its not easy to hold for long term because we'll never know when we can take profit. There's no assurance at all hence we must not invest the money that intended for other important things so we wont be tempted to sell incase of emergency especially if the market is not ideal to take profit already.
What op's said is all true, if you can follow his advise you'll be on the right path on how to hold effectively.