It's a time of many blessings. Grandchildren may come along. Work gets put in perspective. But it's also a time of physical changes, some not so easy to deal with. Eyes lose the ability to focus close up.
Lungs lose elasticity.
The digestive system slows down, so your gut may rebel more often when you eat very rich or very spicy dishes. The idea is to have the end stage of life very brief. We want to die as 'young' as possible, as late as possible. The concept appeals to Iwinski, who makes an effort to stay in shape mentally and physically. In many ways I feel young.