Donna found this article on the importance of good posture — for your health and well-being, and even your safety. It applies to all generations, including those kids you see every day, laboring under their backpacks and peering at their cell phones.
My own experience is that it’s not enough to want to stand up straighter. The muscles you once used to do that may be just too weak. If you’re worried about your posture, you should ask your physician to prescribe a course of physical therapy. The therapist will teach you exercises to help you regain muscle strength.