In this interview by WBUR, research on why older people have handled the pandemic better than younger people is discussed. One of the quotes I found interesting was why people become happier with age:
“There are two sort of principle explanations that dominate the literature, and one is that goals change with age, that people focus more on the present, savoring life, and looking for the positive in life. And another explanation is that older people are better able to select their environments and the people they interact with than younger people are, and so they can control their environments better.”
Planning before and into retirement is the key factor- which leads to this resulting happiness.