Indeed, it can kill you. Part of the reason is that ADD'ers tend to be smart and imaginative, and smart and imaginative people worry a lot. But there are other reasons worry tends to sink its tentacles into the ADD brain more than into others. ADD leaves us facing potential danger, if not disaster, all the time. The wise worrier uses worry as a danger signal to take action on, as opposed to ignoring, or just brooding over.
Wise worry is a key to success in life for everyone, really.
You don't have to be paranoid, just vigilant. Watch out for danger signals, and when you see them, take corrective action. Don't just brood. Your mind will play tricks on you, your imagination will lead you into dark forests, you will get lost in worry after worry if you are not careful to avoid toxic patterns. This is by far the most important principle.