What the person loses is the money used to bet, not the potential winnings that he can cash out. Even if he chooses to cash out, there is still a chance he will lose everything due to greed and not wanting to stop playing, as this is often experienced by players who are too excited because of winning.
Your financial status is more essential than your potential win in deciding if you should cash out or not.
Always use money that we can afford to lose so that when we choose to cash out or not the loss is an amount that we can afford to bear.