There is a lot of ways that someone can interpret the saying "only bet what you can afford to lose" but people cannot really decide on how much is too much. Especially during high adrenaline events like betting.
They should set their limits beforehand. For me, they should never spend the equivalent of their salary in just one bet. You should only bet with your extra money not your entire paycheck of the month. Because if you lose, what will your plan be then? Some only takes 1%-2% of their salary but it depends on how big the salary is
You should always gamble with the amount of money you can afford to lose, which you can safely get out of gambling even if you lose, you should never use your necessary money in unexpected risky places where you have the highest chance of losing.
Gambling, where you only go to find entertainment, is nothing more than this, but if you expect too much and use more money than you can afford in the hope of achieving a big win, it can definitely bring terrible disaster, because you can then naturally lose.
So gamble only with the amount of money you can afford to lose, and if you lose it, stop gambling immediately, because uncontrolled gambling here can lead you to a big disaster.