3.. You aren't willing to wait.
This crazy volatility can shake out many investors. However, some biotechs take years to achieve their potential. If you aren't willing to wait for success, biotech investing probably isn't for you.

MannKind (NASDAQ: MNKD ) presents a textbook case for the importance of waiting. The company first attempted to gain regulatory approval for its inhalable insulin product, Afrezza, back in 2010. Then in 2011, MannKind received another thumbs down from the FDA. Shares have risen and fallen more than 40% multiple times in the meantime.

However, MannKind is now near its third attempt at approval. The stock has more than tripled so far in 2013. Investors who waited patiently could finally see Afrezza gain approval within the next year. Those who didn't wait likely experienced significant percentage losses.

http://www.fool.com/investing/general/2013/06/13/3-reasons-you-shouldnt-buy-stocks-in-biotech.aspx