You mentioned your friend started at $100 usd and manage to have a balance of 24 ETH, so we can't tell if that amount is big enough already that would make him stop as you don't mentioned on your post. If we based on the current price or let's say we will price 1 ETH at $150, then your friend would have cash out $3600 if he have stop.
but like the famous song, don't count your money while you are still on the table, there's a lot of counting time after you gamble.
It means you only win if you made a profit when you stop.
In an addicted person, that difficult to advice them to stop on the usual habbits. They don't even think about what future might bring, if there's money then it'll have to be spent and didn't even bother losing it with gambling. Once a winning profit comes, they'll become unstoppable and more aggressive.
Addicted gamblers don't have the right mentality in terms of when to quit and how to take advantages of certain situations, they are only care of keep pushing forward.
Yea, but that is typical nistake many gamblers do. After they lose big time they think the next bet will be the wining one and they will cover complete loss and make profit above that. That is, of course, wrong and in most cases only takes them even deeper into loss.
Such a feeling that every next time will be win takes you over so easy and if you don't have enough selfcontrol you are lost.