I honestly can't imagine how that person would feel if he really lost that much in just one session, if it's true then I'm sure he's not an ordinary person, and it seems like maybe he's one of the conglomerates. But that amount is really huge, I'm a little skeptical of his statement that he could lose such a large amount in just one session, it's really beyond reason and if it's true there must be a lot of pressure that they experience even though they are a conglomerate class it can't rule out that they will also experience some significant pressure for them.
I believe there are people who gamble this much, although the OP story is not clear and there is some level of doubt about that amount, but on a serious note, I have seen people who wager large amounts of money near to this just in one bet slip, like a post that was deleted some days ago here in the forum where some made a bet of approximately $100,000 in BTC on stake casino in just one single match. Lucky for him, the game played as expected.
But in such a case, if the game goes against his prediction, there will be a huge loss in his stake, and the gambler might definitely see that amount as nothing. For someone to gamble with such an amount, they will really be worth a lot, which makes that amount, which most of us see as a big amount, something small for them. Most gamblers are just determined to take risks; ordinarily, one can't just imagine wagering that amount.