Perhaps you were too rash in deciding to quit work so early in life.
Here are the things you are missing out:
1. Free medical cover (including H&S benefits) for yourself and family
2. Employer
CPF contribution (almost $1k pm or $12k pa)
3. Annual leave (for me, this comes up to 28 days per year)
4. Company sponsored courses, seminars and other in-house training
5. Overseas business trips (on business class) - of course this depends on the work nature and your position in the company
6. With overseas trips, comes overseas allowance over and above your regular pay
7. Bonuses. Typically 3 months (not including the 13th month). On good years this can be 6months or more.
8. Transport claims for private car
9. Colleagues and work social circles. These enrich one's life greatly
10. Have people reporting to you (while you report higher up)
11. Public holidays. (When you are working, you really appreciate public holidays). Now that you are retired, I supposed every day is the same whether weekday, weekend or public holiday.
12. As long as you are needed at work, you have a sense that you are still useful and contributing to society.
The list goes on.
That's why, at 55 and financially prepared, I still prefer working. When you reached a certain level in your company, you do have some autonomy in your work.
Happiness is one of the important ingredients in sustaining what we do. I have worked 30+ years in the same company.