I have one friend who used to play dice in stake.com, he started with a very small fund ($100), out of that money, he managed to have a balance of 24 ETH at some point but unlucky guy lost everything in one day. Once again, with the bonus he got from stake, he managed to cross 30 ETH within less than a month but yesterday, he lost everything once again.
How come he lost everything one day? Do most of the gamblers lose money in such way?
The reason why we should limit ourselves when we are gambling your friend already have a great profit but due to being greedy he loss it all.
I don't know why there are some who wouldn't take out their money once they already won in gambling it would only be a small transaction fee to do it.
If your friend have done that then I think he would still have a great profit on his hand not to mention the second time that he actually pull another huge profit.
The way I see it he believes in his gambling skill and wants to get more even if he already have a huge profit on his hands.