Likewise in gambling, the summary of it is to trade only what you afford to lose.
My addition to it is to strengthen your emotion.
Gambling and trading are way too different. I think that trading becomes uncertain just because of the down market.
It is just something that is never perfect. But, you do not always loose in trading. It is a mater of the market cycle.
When the market is good enough with the prices of some of the coins rising, it is always a perfect time to trade. Like the present market which is expected to rise in days to come.
I don't think he's comparing gambling and trading dude. He's saying that there are certain aspects that are applicable to both, like only spending money that you can let go. And he's right. Both gambling and trading have uncertain results and big risks and it involves your hard earned money. Panic selling is a result of seeing money you can't lose being dumped away.