Maybe your sister went through your things - part of her style while you both were growing up? It's not ok for her to go through your things. Maybe your father over-reacted - out of his surprise about what confronted him about your having cigarettes? The home, after all, is not yours - so if he doesn't want smoking in his home - maybe better listen to him. If you smoke elsewhere - that is your decision. Smoking is expensive, and it can be a health concern - so maybe these are aspects that contributed to his anger (because now he had to face the issue of smoking and respond). Smoking is also a potential fire hazard - what if you were smoking at night and fell asleep?