Why you should run a business
... at least once in your life.
First things first: I don't think being self-employed is a goal for everyone and running a business doesn't mean that you have to do it full-time.
I think everyone can start a small business and should do this to learn a lot. In my three years of working for my own company, I learned so many different things and was faced with so many situation that I learned so much more than in my career before.
In my opinion, you have to be careful with your first business. I'm a software developer and a consultant so my first business was something that I built on my own and where I didn't invest much money. The only financial investments were the registration of a single-person company for 20€ and a basic setup with an accountant that costed less than 1.000€ a year. After these things were in place, I was able to do whatever I want and build on this foundation.
It's important to start small and don't go all-in with a huge investment that changes your life. If you are in debt, things can become a huge problem very very quickly. Start with a side business and decide where to go from there–you can even decide to shut it down after a few months–but make sure you don't shut it down when you are facing the first difficulties. If you shut it down too quickly, you don't learn the lessons that are the whole point.
Many people are complaining about their boss or their employer if it is a bigger company. They don't think about all the things that a company owner has to do and that running a company with employees costs a lot of money every month. They don't think about the fact that this money must be earned by providing some form of value to clients or producing goods which other people buy. They only see their own situation but have no idea how the whole picture looks like. Sometimes their boss doesn't share the picture and in other scenarios, their boss doesn't even know the picture–but as a boss, you are responsible for everything. So if you run your own business, you are the boss and if you don't sell the things you make, you made a wrong decision and can't blame someone else.
So even if running a business full-time is not your thing and stresses you out, you'll learn a lot and view decisions of your boss from different points of view from now on. This is why you should run a business at least once in your life.