The quality of your idea isn't the only factor that will determine the success -- or failure -- of your startup, writes Lindsey Guest, founder and CEO of Beauty Army. "The bad news is that the idea is not even [0.1%] of the difficulty of being an entrepreneur," she writes. "Great teams can make a bad idea work and bad teams couldn't make a paper plane fly." It's important to trust your instincts and to be flexible as you build your business, she writes.