This method is also quite safe, but it does not guarantee a consistent bet amount for each game. Because most of the money you win will be less than the amount you bet, right? For example, if you bet 10 coins, you win 8 coins, and use those 8 coins to bet on the next bet, then clearly the amount you bet in the 2nd game is not equal to the 1st game, so the bet amount will be inconsistent, it will be difficult to control the account later.
I think you should not care too much about the amount of money you have won, just focus on maintaining a consistent betting amount. After a certain period of time, it could be a week or a month, you should summarize it once to find out what your win/loss ratio is. From that result, you can adjust your bet amount to be more reasonable on the next week or month.
Everything will have risk so we must knows how to minimize the risk of losing. If he thinks that he can used that way, he can still used it but he must discipline with that way and not increase his budgets or his bets. Maybe he can used small bets in every bet he placed and do that every time he wants playing gambling with a certain budgets. He must follows his own rules and limits his budgets so he will not used more money to playing gambling. He must remember that playing gambling can makes him used more money and his job is prevents that happens or he will regret it when he lose all of his money. We must overcome the losses that may happen and only with limitation that we can do to avoids a big lose. He doesn't have to thinks about grow his money from gambling because that's difficult and not many people can make money from gambling.
Yes, especially if it involves money or that means especially if something you do involves your money, plus as we know, gambling has risks where the level of risk can sometimes be very large when someone cannot control themselves in gambling. On the other hand, of course, as you said, discipline must really be applied to gambling involvement, apart from that we also must not ignore other aspects which are no less important, such as control and placing limits on two things, namely time and budget.
Because there are only a few things that can keep us from avoiding the bad possibilities that exist in gambling such as losing larger amounts, and the other thing is that we really have to be able to maintain our awareness of understanding the concept of gambling, or that means we have to always remember that gambling can lose everything we have when we try to do something that is too careless and risky, and by having a good level of awareness then I am sure you will not be careless in making every decision, such as always keeping a small amount or always limiting the time for gamble. Gambling is not a place to make money because there is absolutely nothing that can guarantee you will always win, therefore it is better for us to prioritize things that can prevent us from worse possibilities.