Losing money when in blinds

According to my stats I am losing way too much money when in blinds. Of course; I play hands that belongs to the muck if it wasn't for the forced bet, but... I figure there is more to it.
I recently begun analyzing my statistics, and this lookes like one leak that needs attantion.

So, to my question. What is the most common mistake playing in the blinds? Folding to easy when faced a raise, or defending the blind against possible steal attempts?

Any comments welcomed. Thanks in advance.