Yeah, it's the best solution for him to re-assess whatever mistake he made during that failed session, instead of pushing his way to keep playing and most of the time the outcome will be against him, you need to be wise to keep that emotion and treatment towards your gambling participation, having that kind of understanding will let you to keep yourself in shape.
By introspecting ourselves on the mistakes we have made before, this will certainly motivate us to be more careful in every decision and action we take in the future. For wise and responsible gamblers, have good thinking because opportunity does not come a second time and this can be applied in gambling so that we remain consistent in maintaining good control.
He can check any mistake he made to know how to fix it, and it needs patience to search for the way to change himself not to be like that when he lost in gambling. That's normal if someone behaviours change based on what he faced but doesn't mean someone will still be like that, especially if that person realize that his bad behaviours made him feel guilty about what he made before. That's why awareness is necessary needed for every people, whether they are gamble or not gambling to do something because that can make other people feels not comfortable with him. Introspecting ourselves purposes to know and identify the mistakes so we can fix and change to have a better person. If we can do that, we can suppress our emotion not to doing anything that can make us feel bad after we realize.