I assume that people come to the gambling industry as inexperienced people. And in the process of their activities, they gradually learn from their mistakes. Unfortunately, some of these mistakes are dramatic and cause us quite serious psychological trauma. As a rule, this is due to gross errors and stupid persistent beliefs that push us to the edge of the financial abyss.
First of all, this is risk management and money management. The second is probably unsystematic play. Let me make a reservation that I do not mean casinos, as well as people playing "for fun". I mean sports betting.
So, how much did your mistakes cost? Did they cause you a serious psychological blow? What were your mistakes, did you learn from these mistakes and do you apply this knowledge in practice now? Were these mistakes simply painful, dramatic or catastrophic?
I'd say that it's never wasted money as long as you learned something from it. The greatest entrepreneurs and business people will tell you that they had the tenacity to try many different things over time in order to figure out what worked, then when they had something, they gradually lost less as they refined it into something profitable. It's difficult with sports betting though, because you have an opponent (the bookmaker) who is constantly evolving to counter your plays, as that is what makes a profit for them. Painful blows can be the most beneficial as they can sear in a memory that you are less likely to forget, but be careful not to overstretch yourself as that is likely to lead to burn out and prevent you ever wanting to participate again.