Smoking People

Yesterday I have in a room where people where smoking for 2 hours. I have had extreme pains in my throat, belly aches, headaches and I can't properly breathe since. I wonder how do you people put up with this kind of stuff? And also a question for the people that smoke here, I just wonder why to be honest. From what I have seen in my family it has killed an enormous amount of people. I just wonder how you started with it and what your motivation is to keep doing it(besides addiction)