Mistakes is the salt of life. Without mistakes we will not learn anything from this life. And mistakes in business means losses. Small losses, i think, necessary to learn from your fault and not to fall in the hole again. But i think big losses, like 100 0$, destroying you and making you even hate to continue with that business. I know indian friend who lost 1000$ in betting, guess what, he give up the whole earning tools in the the net and turn to school study.