Most start up companies will fail, its just a fact. Unfortunately for some, that means lost cash. Even for those companies that don't fail, there is going to be a period of negative cash flow and thus, forfeited capital. While its never a good thing to lose money, I would encourage people to remember that the U.S. Government wants you to start businesses and thus, has a made some tax advantages for those that do so.
I wont go into too much detail because I don't pretend to be a tax expert, but I will offer the overarching idea. Basically, if you start a business and it goes south then the business losses can be used to offset your tax bill for the year. For example, lets say you make $100k a year at your day job (nice job right) and you owe $40k for taxes. If you started a business and lost 10k then some of that loss can be taken against your taxes and you will owe the government $30k. Now its not that simple and the numbers don't work out quite so cleanly, but the basic point is that the huge fear of loosing money in a business may be mitigated for some, to some extent, due to tax advantages.
Also, there is the added benefit that you can write off many deductions for your business as the money your spending are "business expenses". Just a thought. Google this stuff and talk to a tax person, but don't be as scared of loosing money, because there are some tools in place to help you out.