The Downhill Slide to Death

Before we're 20 years old I think the body stops growing. At that point although it doesn't seem like it through our 20s and 30s what's actually happening is the body begins decaying. Reflecting on how far away from your late teens, your early 20s you are, how long have you been decaying this body? How long has the downhill slide towards death been happening? Maybe you're only five or ten years or into it or maybe five or ten or five or six decades into it. What are the signs, the feelings, the sensations of aging in your body, if any? How is it changing?