How hard is it to start and run one's own businesses? What's so hard about it?

The fact is that once you become successful in your career, you will find yourself in a position where you can not afford to quit and start a business of your own.

You've got the mortgage, the kids education, back taxes etc.

Like most people in our modern consumer culture you have probably become used to spending most of what you earn.

So there is no money left to support you while you start a new business.

Running a business involves a lot of other skills than the ones you are used to using. Specifically there are a lot of marketing and sales activities. If you are highly introverted then you will want to find a partner who can compensate because you just won't feel comfortable doing the type of work that an extroverted person loves

It is extremely difficult. More than 50% of businesses fail in the first year. Of those left about 30% fail in the first 5 years. It takes a good plan, a unique selling point and tons of hard work. Plus, you as the owner are responsible for everything. No time off. However, if you are successful, you get to keep all the profits.

It's really easy. But the stats are worse than for first-time marriages. Biggest problem seems to be under-capitalization. If you are considering this course, read all you can on the subject, both from the business side and from the side of the specific business you want to start. Then talk to others who have been successful in the same line. Ask them what it took. Then read some more. Then pray. Then raise about four times more money thatn you think you might need. DO NOT try starting your business on a shoestring and sweat equity. And, good luck.

consider that 80% of self run business fail within 5 years

well depends on the biz. I have a side biz building computers for people. My main hardships were inventory(now depleted due to moving lol), advertising, and also setting up warrenties, and return policies.
Now if you're talking forming a car company, phuggetaboutit, GM, and Ford will spearhead ya. it all depends. :)

Location,product,customers,bookkeeping,bankruptcy.