Take it from someone who has a couple of toes in the self-employment industry. Being self-employed is very rewarding, but it’s also a lot of hard work. There are a lot of issues around Self Employment and you must consider them carefully before going down this road.
Its All On You - This isn’t an understatement. You are very must responsible for everything, especially in the early days. Its very important to have a solid business plan before you even think about getting things moving.
Why will your business/product appeal to people?
How do you plan to create said business/product?
How do plan to reach your target audience?
What are the costs, and can you afford them?
Is it worth the risk?
These are the questions to ask yourself and you must think about the answer carefully before weighing up your options. Becoming self-employed means you are investing in your self and that usually means money. If your business planned failed will you still have money to support yourself, do you have a job to go back to?
You hear many stories about people who quit their job to follow their dream and were very successful. You very rarely hear about the ones that failed, so its easy to be fooled into thinking self employment works for everyone and makes the rich. It doesn’t.

Comments
You are so right about having that initial business plan! Being brave to hang on in when the going gets tough is also important.
You also have to be willing to take on a lot of paperwork and learn lots of new rules and regulations. You'll be responsible for doing your own accounts and tax returns (unless you are successful enough to hire and accountant to do them for you) and when you expand and start hiring people you will learn how complex employment rules can be. Not for the faint-hearted.
Don't get me started on tax, just thinking about it makes my head spin. Think that needs its own page.