if you approach it with the idea of entertainment only, like the idea of going to a movie. and spend 15 bucks on it every once in a while... gambling wont ruin your life anymore than World of Warcraft will. But if you like most people and cant control yourself.. you have to be careful and the best advice is to avoid it.
In gambling it will all depends on the gambler on how he/she react when on loosing streak or loosing side. Some of them will chase the losses and will only lead to loosing more. Proper discipline and control of a gambler is a key so he/she won't end up broke or loosing big amount of money. Gambling recklessly will lead you on wrecking your life.