Is using a Credit Card useful or dangerous???

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I've been hearing a lot of people around that using credit cards are not so helpful. In fact, upon using credit cards is like a drug, once you used up, you pay the price where you payback its debt on a monthly basis. Whats worse about it is its penalties or its additional fees. But others would say its helpful because you can use it in case of emergencies only. So, whats your opinion on this??? Any thoughts???