I wouldn't term it as a good or bad advice because of a simple reason - destiny! I strongly believe that destiny drives us all and if destiny says that I will die as a billionaire, I will become one! We as a commoner, don't know how and when a coin will reach its ATH and we wouldn't know when to sell it off to book profit!
You're very right about that destiny. Destiny is what drives everyone, anyone that is meant to be rich will one day become rich no matter what. It's not everyone that is rich today that became rich through cryptocurrency. The world's richest men we know today, none of them had anything to do with cryptocurrency, rather they were into businesses that are completely different. So no matter what you're into, you will always arrive where you're meant to be. And that's the truth and nothing else.
My point is its bad selling off all your coins, if you needed money that bad always leave coins and tokens worth of few dollars left in your wallet just in case
Man you will never understand. Sometimes, people have no other option because that's their last card (money), and they need it badly for solving a problem that they are having at that moment. You can only be able to store money in your cryptocurrency wallet when you have enough to do so, and you know for sure that you can leave that money there without worrying about whether price is decreasing or increasing. If that's you, then you invest an amount and leave it there for years or till the next bull run happens.