So you've thought of a product or service that you can sell. You've done your market research and have decided that a business is feasible. You've looked into the costs of building your sales channel, the costs of administration, the costs of insuring yourself, your company, and your employees. You've looked 5 years down the road to see (realistically) where you could be, and you've extrapolated all those costs and profits, sales and losses into some form of business plan.
What! You mean you haven't? OK, then you need to. One at a time, and carefully, with an objective head, not the passionate one that thinks you product or service is going to be wanted by everyone.
Wow! You have! Well done. Now what? Take it easy! go slowly and follow your plan. Don't deviate from it. At the end of the first year, if you are still in business, analyse your plan again. Go over everything. Be realistic. Build into that plan some business strategies. Watch your overheads. make it a date, do this every year, and more often if your business grows rapidly.
Don't make big changes to your business model, add to it, yes, but don't change it.
Stay lean, and I don't mean fire everyone, make sure you are getting the best out of every single overhead and investment you make.
If you get in above your head, ask for help, and where you can, get it free. Get a second, third, fourth... opinion. Don't aim for failure, but don't be afraid to fail. It's not the failure that defines you, it's what you do afterwards.
If you are lucky you'll get rich/famous/happy whatever you want. If you are not, you'll get experience. In either case, it won't come easy, and it won't come quickly.
Good luck and happy hunting!