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?
First of all, we should know that no one is above mistake, we are going to face the consequences of every mistakes we made, some may come as a costly one while on the other end, we may manage to scale through some as the case maybe, but being a newbie, the desperation to win is always there and once they got the idea wrong, they begin to miss out on opportunities until the priority is well set as to what gambling is, which everyone eventually learns from the mistakes they did.