If you lose small amount then the chance that you can still control your emotion is very possible unlike if you using huge amount which most of the time carried your emotions, when you lose you get aggreviated and you wanted to recover quickly, meaning that you'll add more money and probably the outcome still against you.
Better to stop and make sure to analyze, re-assess if possible and take some air chill yourself that helps to refresh your intention and avoid losing more.
Hmm, I myself think maybe it depends on us how we think about gambling itself, if our mindset responds to gambling as just entertainment then the amount of money lost will not be a problem but when our mindset considers gambling as a way to make money then the amount of money lost will affect our emotions and it can continue.
You are right, whatever the situation whether winning or losing then it is better to stop with the aim of calming down. Also, don't forget to do research first so that we don't have the wrong mindset in responding to gambling.