Smoking
I started smoking when I was 21, three of the guys I worked with were a heavy smokers. I would get bad headaches on my days off & if I was in a restaurant or elsewhere & someone lit up, my headache would go away within minutes. So, I bought some & I would light up to make the headaches go away. By the time I was 23, I was up to two packs a day.
I quit cold turkey on my 24th birthday & I have never wanted another one, that was over 22 years ago.
Three of the guys I worked with back then have been dead for years, all due to smoking related illnesses. The other 'survivor' on that crew was also quit smoking not long after I did.
Best of luck! You can quit if you really want too.