How hard is it really to start, run & maintain a sustainable business?

Hi everyone,

I'm a wantrepreneur (had some side projects that made some money) but am working as a full-time employee right now ( hate it 100%).
I was wondering what your experience is in starting, running & maintaining a sustainable business.

My goal is to replace my job with running a sustainable business overtime.

What's your experience with it?
(Preferably only people who are full-time entrepreneurs themselves and run or ran multiple businesses.)

Thanks!

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