Being in business has taught me a few things over the years. Here are the most crucial.
You cannot control everything — It's easy to think that once you're the boss you can command and execute your plans without hesitation. What you might not count on is how everyone else fits into the plan.
People might promise to pay and don't, errors can be made on jobs or quotes, you might have a customer leave and not know why. You need to make sure you can move on and let these things go. Practise making peace with the things that stress you out.
Your price point is important — How you charge is essentially how you value yourself, your service or product. If you give all your stuff away for free or for very little you'll have no money to pay your own way.
Make sure you know your numbers, the income you need and costs you'll have and then ask yourself about what's left over — is this good enough for the goods and services I provide? If you're not earning as much as you might if you were employed by someone else, are you getting other benefits from your business?