Not necessarily "reduce that activity" although I would recommend it anyway, but the fact that you always have to make sure that everything is in routine behavior. For addicts and people who have already fallen into the gambling addiction spiral, the best way for you to gain your control back isn't to outright stop from gambling, you'd find withdrawal to be your biggest hurdle and enemy. The best thing you could do for yourself is to create a routine first, for how you would manage your gambling sessions, slowly diminish it over time, replacing the time you could've spent gambling with more productive hobbies instead, and gradually you'd find yourself rid of the gambling addiction stink.
Of course this isn't going to work for everyone especially those that have fallen into destructive behavior, but in a general sense, this is one of the best things you could commit to if you really want to stop gambling.
Yeah, I also thought if they stopped right away, it would confuse their bodies and tell them something was wrong with this. Maybe they can start by slowly reducing their gambling activities so that their bodies and minds can adjust to these gradual changes. And besides gradually reducing their activities, they need to do other activities so that their minds are awake and not thinking about gambling. Over time, if they keep doing their activities routinely and trying to reduce their gambling activities, they will see that they have succeeded in reducing their gambling activities. And finally, they can stop playing gambling and can be free from gambling addiction.