This is not a fact.
Just because we all die at some point, doesn't mean we don't have to live a worthful life? "Ahh just smoke, we all die, whatever" hope you can see how stupid this really is. If you have any family or friends (or upcoming), this would be everything to live for. The thing you said about your granddad is not a fact, but just a coincidence really. If you like to smoke, that is your decision, not mine and I don't blame you for that at all.