a/your second childhood
1. A time in a person's life (especially an older person) when their mental capacity is reduced to that of a child, as due to disease or old age. After my grandfather suffered his second stroke, he really entered into a second childhood.
2. A period of rejuvenated or renewed interest in things that interest a child. Being a part of my son's life as he grows up has been like a second childhood for me, because seeing him experience the magic of the world has made me appreciate it again as well. Jerry's sort of been in his second childhood ever since he lost his job, as he's gotten back into model train building and video games.
The dotage of old age; also, childlike playfulness in an adult. For example, Grandpa needs full-time care, now that he's in his second childhood, or Since he retired and started learning to fly, he's been in his second childhood. Depending on the context, this term may allude either to such problems of old age as losing one's mental or physical capacities or to delighting in new pleasures in a childlike fashion. [c. 1900]
1. An adult's second childhood is a period of time when they have fun and do things that children typically enjoy. My father was a model railway man. My mother passes this off as his second childhood.
2. An elderly person's second childhood is when their mind has become weak and they can no longer care for themselves. We were shocked by his rapid descent into a second childhood.