There are two people I know of whose work is useful for exploring the theme of personal happiness construction. One is a psychology professor at Northwestern University. That's Lisa Barrett Feldman. The other was an employee of Google and that is Chade Meng-Tan. He is the author of "Search Inside Yourself" and "Joy on Demand". It is this latter book that relates to being happy most of the time.
https://chademeng.com/about/bio/
There are more books and other instructive materials coming out all the time about using one's mind to be upbeat about life.
Prof. Lisa Feldman has some TED talks. One is titled
You aren't at the mercy of your emotions -- your brain creates them
She is also the author of the best book I know about our brains and living with them, the book "Seven and a Half Lessons about Your Brain".
It may be that many older people have a natural tendency to supply themselves with good emotions but if not, read, watch and practice.
