Personally I think, the cause of this is panic, afterwhich they realize that they just lost an amount that isn't ment to be used for gambling.
So my question is:
How would you best advice someone who is still trying to protect their loses?
You cannot protect you loss, you just have to live within your limits.
What many gamblers don't know is that the more you try to play safe, the more losses you will make. Pick a risk, stick to it. Don't add or reduce the amount you risk every time. Don't chase after your loses. When you exhaust you budget. Call it a day and wrap it up.
Then most important element to preserve inn gambling is your deposit. Without it, you have nothing to gamble on. So instead of chasing loss, be your best at risking deligently. Don't panic or over react even if you still mess up, be at your maximum composure.