If one is not interested in the rocking-chair version of retirement? Here are some alternatives to choose from.
Instead of working ceaselessly and then stopping permanently, consider working and saving for several years, then taking 6 months to 1 year off to travel or explore new horizons, then return to work for a few more years, then off again for some months to pursue another passion for a while. Consult a financial adviser about the best way to prepare for this on and off approach to retirement.
After a lifetime of developing your career skills, you are uniquely qualified to give back to the community. Consider mentoring youth groups or individuals, volunteering and community work. Perhaps with some paid consulting or part-time work on the side.
You've loved your work so much so instead of retiring completely, you move your practice to part-time and go back to school, but this time study for pleasure or just for the knowledge, if you are a doctor you might decide to study law….
Say you've been an accountant all your life but always wanted a career in education, you can teach math or author a book, or whatever. Retirement time is a good time to start a career in a field of interest.