I am 72 years old, in good health, but having difficulty dealing with getting old. I have everything I need in life but I am not happy. What is wrong with me?
Maybe your problem is that you "have everything you need in life."
Try challenging yourself in some way. Learn to play a musical instrument or learn some other skill. Become an expert at something, just for the hell of it.
Or look at the PERMA model for happiness...
P – Positive Emotions
Positive Emotion is much more than happiness. Positive emotions include hope, joy, love, compassion, amusement, and gratitude. Positive emotions are a prime indicator of flourishing (Fredrickson, 2001) and can be cultivated. However, this does not mean we need to repress negative emotions. Instead, we can accept all emotional experiences but expose ourselves to situations where positive emotions arise naturally.
E – Engagement
According to Seligman, engagement is being one with the music (2012). Engagement is similar to the concept of flow. It refers to a loss of self-consciousness and complete absorption in an activity. It is mindfully focusing on the task at hand.
R – Relationships
Relationships encompass all the interactions individuals have with partners, friends, family members, and their community at large. This part of the model refers to feeling supported, loved, and valued by others.
M – Meaning
Meaning is defined as belonging and serving something greater than ourselves. Having a purpose helps individuals focus on what is important in the face of significant challenges or adversity (Seligman, 2012).
A – Accomplishments
A sense of accomplishment results from mastering an endeavor and working towards goals. Achievements contribute to wellbeing because individuals can look at their lives with a sense of pride.
https://positivepsychology.com/perma-model/