A early rich retiree
should be the happiest of all. He doesn't have to work. He has all the money he needs. He can do what he likes (as long as it is legal and appropriate).
We all are stuck in web of relationships and needs.
You have responsibilities towards yourself, kids, spouse, family, society ...
Your body(and mind) needs food, clothes, shelter, entertainment...
Why are you here? Because your parents decided to have you. While it is very tempting to investigate any other reason for your existence, this might be the only real reason.No there must be some bigger reason
If you believe in God, he intended to create earth and all the life on it. With all the related philosophical reasoning. If you don't want to believe, it might be that life happened and as a series of cause and effects you arrived.
Anyways now that you are alive, is there a script you need to follow? ("What should I do in life").
There might not be anything that one "has-to" do. It is just that you are part of this universe with planets, life et al. There is no "perfect" reason for existence. Though there are million reasons that humans came up with. You can either agree with one or many of those reasons (religions !) or come-out with own reason or live with a possibility that there is no big reason for existence.
First in the line of responsibilities is yourself. Then comes kids, spouse, family, society, life, universe etc.
For yourself you need to keep yourself alive, entertained, growing, painfree, happy...At the same time you are to address other responsibilities.
Somewhere embedded in all this is your job.
Job is just a part of life (with pains and pleasures). Job contributes to both pain & pleasure. Often only the 'job' contributes to much of pleasure (and pain). So in a sense job makes you alive (active).
You can choose to become inactive (retired) or change the activity beyond (and possibly in place of) job.
While no one really dictates that you be alive, the best thing for you, family, society, universe ...is that you be alive. As long and as much as possible.
So retirement is not ideal goal, finding ways to be fully alive is. Maybe that is "Nirvana".