Why do some get addicted to things that they know could kill them and sometimes does? Like drugs, alcohol, smoking?

I was addicted inadvertently once upon a time long ago. I had a weight problem for years and one doctor gave me DIET PILLS to take. Worked like a charm. They energized me and cut my appetite. I lost weight effortlessly. When the doc said I'd lost enough weight I asked that I still be able to get the prescription filled because they gave me so much energy! Of course that was not a smart thing to say but actually it was or I'd still be taking them. Of course he said no. It took me two weeks to come down from it and those two weeks were the most miserable of my life. I guess they didn't know amphetamines were addictive. Kicking that addiction was gawdawful. The weight problem went away and now I weigh to make sure I'm not losing weight. Once you get cancer and beat it losing weight without trying to is an indication that something in the body is not working right and it may be an indication the cancer is back. So I weigh every day hoping my weight is the same. Weird irony isn't it? Spend years worrying about gaining weight then spend years worrying about losing too much. Go figger!  Thank you for your reply Kg! :) This post was edited by RosieG at February 20, 2021 9:08 AM MST