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It should be this way only where you only play when in mood or just when you are invited to to meet your friends. Not that every week you end up in a gambling and then realize that you are hooked up to it and cannot stay without gambling.
Every week or even everyday is fine as long as you stay on your own limit on each play. It is better than you play once a month or even once a year but you play over your own limit. They key is your own limit and yourself, no matter how often you play, as long as you stays on your limit then it wont be bad thing for you.
It won't be a bad thing regarding your finances, I agree with you on that, but I think another thing which should be considered is time. Even if you are playing in demo mode losing no money at all, you still can lose a lot of your time, and that thing should be avoided too. For example, some poker tournaments can last for 3 hours or even longer, and if you decide to participate in more than one of such tournaments during one day, I think it's too much. Gambling is a good entertainment, but constantly entertaining yourself is not what life is all about.
Wasting too much time on anything, especially in gambling, could make us lazy. This is one of the starting points when we become ignorant of other things in our real life that are very bad for our future. So gambling will affect not just our finances but also can change our behavior at the same time if we do it excessively.