This goes with trading too. With demo account you are willing to sacrifice everything because you know there's a "save point".
The problem is, what if you got used to that perspective and habitually done the same thing over and over. From losing more, you also lose the "will" to continue trading and that sucks.
You gave a very good analogy. Indeed, starting anew every time, this can lead to sad consequences. In trading, there is this type of people who, when they lose their money, make a new deposit and continue to do the same, hoping for a different result. I think this is no longer trading, but gambling addiction. In addition, the trader may begin to have an irresistible desire to try to recoup and compensate for all past losses, the risks increase and the martingale begins to be applied. And all this is already turning into gambling. If a trader gets excited, then that trader will never do well.