However, if a user gambles only for fun and can't control himself during losses,
IMHO, those gamblers that are doing it for fun have even the control than those that are gambling for profit.
he should choose a casino with a feature that forcibly restricts access to gambling, either by time or by the amount of money lost.
Duelbits have it as well the self exclusion and if someone is struggling to control his/herself, they've got that feature to know more about it. They've made an article on how it can be done:
Self-Exclusion from Duelbits