During my colleges days i often gamble with my friends and sometimes i would skip class just to gamble with them, it took a toll on me when i didnt get enough grades on a class which a often skip, since that day i stop gambling and finish college then find a work and gamble once a month.
It's great you saw it quite early and quit to pursue your studies more seriously because many get entangled between studies and gambling and the weak ones often give up their studies to gamble for money and are often plunged into addiction.
You just live in the wrong environment, gambling never be a good habit for those people who didn't earn money yet by themselves, they tend to do it irresponsibly. No wonder they do crazy things that doesn't makes any sense like skipping something important for the sake of gambling. You should looking for a real help when it's happened.