A friend of mine is smoking and they don't know that I know. What do I do? Do I live with it?

1st.: is your friend a minor? if so, then:
2. your friend may be having a hard time with something (people don't just start smoking out of nowhere). Also, he may be influenced by someone else (a friend that also smokes, or a group of friends, or even family members).
3. Don't panic. Even though cigarrettes are very toxic if stopped in time there is no real damage to the body. It's a slow death basically (sorry if it sounds horrible, but that's the truth). I think drinking alcohol in the same quantities is even worse, and people do it anyway. Take care of your friend and remind them that they are important to you. If they don't change their behaviour there's not much you can do about it, sorry. If they want to smoke they will when you are not around. You can't be a "hero". I hope this helped in some way.

Don't impose on someone process of growing up. People make mistakes all the time. People make bad decisions and sometimes they know it, sometimes they don't. T has nothing to do with you, so don't make it about you, otherwise their process is stunted, only because you have to have things your way and youre sure you are in the right. It's a good way to lose friends.

Practice acceptance, forgiveness, and turn those sights inward. Let people live their lives and grow at their own pace, and worry about your life and your growth. Being someone who doesn't make bad decisions doesn't give you the right to interfere. It also doesn't make you a good person. It doesn't make you the example. The only person you need to worry about is you. Good to start with why its so important for others to behave the way you want them to, and why you aren't willing to observe and criticize your own behaviour.

PS you did well to come ask before reacting. But still important to note that you're more interested and what to do about them then why it bothers you and why you feel the visual to do something.

The part of you that hesitated is something to consider always.

That part of you is considering the other person. But the part of you that wants to react is only concerned about you and your own comforts. Listen to the part that hesitates, it will ask you to be a friend and understand before you react. Treating them like they need to be fixed is inconsiderate. And selfish that you believe it's your responsibility.

feel the need*

ye i kinda agree with the person above. not much else to say

Guys I don’t really care anymore so just do whatever I guess. I only ask to stop replying to this thread.