• Eric Sim retired from his 20-year banking career in 2017 after achieving financial freedom.
• But the former investment-bank managing director says he's not a fan of the FIRE lifestyle.
• Sim became a professional speaker and executive coach after he left banking in 2017.

This as-told-to essay is based on a conversation with Eric Sim, 54, a former banker who became a published author, professional speaker, and career coach. The following has been edited for length and clarity. Business Insider previously published an essay about Sim's banking career.

When I started my career in banking, I didn't give much thought to retiring early.

I figured I would retire at age 65 and engage in typical retirement activities like going on cruises and hanging out with old friends.

But things changed after I became a managing director at UBS. After working for a few years there, where I managed to earn multiple annual bonuses, I realized that I was actually financially free.

That got me thinking: If I didn't need to work for someone else, what would I do?

I knew that I couldn't just quit my job without a plan. I needed to find a meaningful project to which I could devote my energies.

After much thought and reflection, I decided to leave banking to run my own training institute for young professionals. I started the Institute of Life in 2015 with the mission of helping young people achieve success at work and in life.

FIRE isn't as great as you think it is

Even though I have achieved financial freedom, I'm not a fan of the Financial Independence Retire Early, or FIRE, movement.

To achieve FIRE, you must save a lot of your income during your working years. But the truth is, people often don't have a clear idea of what retiring will look like for them or if they'll enjoy it — especially if they're in the weeds and working toward it.

Of course, when you first retire, you can do whatever you want. You can travel overseas, hit the spa, or play golf.

After working for 10 to 20 years, being free from the grind for the first three months feels good. But you'll get bored very quickly.

When you are working, you don't have to plan for what you want to do. Your day job will give you more than enough things to do.

But if you are financially independent, without a regular schedule to adhere to, you need to find projects to occupy your time. If you don't do that, then your days are wasted.

A good retirement isn't just about having money in the bank

To have a good retirement, you will need three types of capital. Besides financial capital, you need human and social capital if you want to make the most of your time.

Human capital refers to the knowledge you possess. You can build this up through your career or through your side hustles and hobbies. By developing your interests and skills, you will know what activities you want to do when you go into retirement mode.

Social capital refers to the goodwill you accumulate with others. The small help that you offer to others can come back in a big way when you retire.

Ultimately, you need to know what you want to do after leaving your day job. If there is something that you always wanted to do, and is meaningful, I would say go for it.

But if you have nothing to look forward to and don't have a mission yet, just stay in your day job. You can still pursue your own interests on the side without quitting your job.