People will remain consistently happy as they get older simply understand that what they need and want today is not what they will need and want educate from now so freedom and independence are great when you are young and still chasing who you want to be but then.
As you get older as your values evolve you will be surprised by how contradictory withbyour past self desire can become things that seem so exciting in the past might not be be so exciting again and nothing really matters again.
You just want to uphold your values and set boundaries. That is the result of getting older
and behaving more mature.