Responsible risk in gambling is basically using amount that you can afford to loose, gambling wins are by luck so you need to minimize the risks. We don't have any control over the outcome of our gambling results, the only thing that we have a control over is the amount that we decide to use. The higher the amount that you use for gambling the higher the risks, the lower the amount the lower the risk so we need to determine the level of risks that we're comfortable with. Gambling is not like a business where you're sure of making profit when you put money into it, there is no guarantee of wins so it's better to gamble responsibly by reducing the amount to something that you can loose.
Of course you are absolutely right that's the real truth about it, because that is actually the real definition of a responsible gambler. Once a gambler uses a small amount in gambling it will be very hard for such gambler to chase after losses or get addicted to gambling. Because excess risks of become rich quick through gambling is always the cause of many gambling addiction nowadays. It's very unfortunate that most gamblers still do not understand gambling till now because is quite simple that there is no amount of risks that would easily guarantee you winnings in gambling.