I used to smoke, think worst was just like a pack a week in my teens/early 20s. Mainly for social and relaxation reasons. Started vaping when I was 27ish, felt like a douche, and "quit". Would smoke maybe 2-3 cigarettes a year until I met my wife and completely gave it up. Luckily I was never addicted because while I smoked, I was already prescribed Wellbutrin so I was effectively immune to nicotine addiction.
So glad I quit, and now that I work with teenagers its a shame to see so many vaping so young and think nothing of it. Then again I had the same attitude their age, we just didnt pretend it was healthy.