What's the real reason why you don't want to do it?
I have a really bad cough and My throat is already super soar because im sick and I don't want you to get sick either.
Spit it out, why can't you use it.
So now you know why i cant do it.
Why didn't you tell me this at the start of this day i would've left you alone.
IF you have to you can use medical reasons to avoid using weed. You could say that you get really sick whenever you do it. Or you can say that you don't want to get addicted or that you have a very important thing to do tomorrow. Or just say that you have a lung infection or a sough throat.
As you can see that Henry managed to disarm the situation and make it so that Connor isn't pushing it onto him anymore because he doesn't want to get sick and make Henry even more sick.
Now that Connor believes that Henry is sick he has left him alone and won't be pressuring him to do it.