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?
Can't really remember how much I lost because I made a mistake in believing that I had a sure bet. Maybe it was between $100-300 many years ago. I used an amount that I can't afford to lose, so it was an uncomfortable situation that affected me psychologically. The lesson was that nothing is sure in gambling. Don't ever believe that a team or player will certainly win or lose a game. Always gamble with the mentality that you can lose or win. It shaped me to be a responsible gambler. Although the amount I lost was high considering my income then. But it was just a painful experience and nothing too serious.
Similar to that sentiment, I use to make that mistake betting with a decent amount that I'm not intended to use for gambling but I was move by the trust on my instinct that I'm betting with a team that can really deliver a sure win, only to realize that upset can happen and same deal with you that sure thing messed up and it cost something decent that did not let me to forget for some time,
A good lesson is not to do same mistake again and always use the amount that you are willing to let go, whatever happen it won't affect you that much and will keep you away from too much regret.