The older you are when you smoke, the worse it is for you. Smoking in your twenties is far less harmful in terms of its likelihood to cause cancer than smoking in your forties, fifties, or sixties. The damage gets worse with every decade of your life.
Just stop. In five years' time, you'll wonder why you didn't stop sooner.
Just stop. In five years' time, you'll wonder why you didn't stop sooner.