When the people of today think of the word discipline the first image that may come to their minds could be the army, but discipline is simply to have self-control, so if before you start your gambling session you say to yourself you will only gamble for half an hour, then someone with discipline will only gamble for half an hour or less, extending that time because you are having fun may no be wrong but it reveals a small lack of discipline, that under the wrong circumstances it could have negative effects on your finances.
And in fact, not as easy as we talk. We can adopt "discipline" in gambling, but in practice it is not as easy as we say. the problem is, what we play is related to fun, entertainment, and maybe a challenge. we are well aware, things that contain pleasure will be very difficult to stop. and if I refer to what you said, self-discipline is just to have self-control. i agree with this idea, but the problem is as i said above. that in practice, it's not as easy as we talk. in fact, you have given a little picture as an example.
For me personally, the point is not discipline. but more on understanding, awareness, responsibility and self-control. Gambling is something that is fun, but it carries risks in it. if we understand it, realize it, and also involve responsibility, the result will be self-control. but once again I say, in practice it is not as easy as we say. like in the OP's casino for example, actually OP has received a bid from his 5 wins in his multibet bet, unfortunately OP ignored it and he chose to continue. in the end, he lost the bet. if OP has good understanding and self-control, OP will try to re-examine the remaining two games that determine victory or defeat. if the odds are low, OP can take the offer from the casino. this proves, that in practice it is not as easy as what we discussed.