2007 to 2009 double dips

Let me work on those numbers:

Oct 2007 - July 2008                 20% drop
July 2008 - March 9, 2009         45% drop

S & P 500 lost almost 60% of its value from Oct 2007 to March 2009

I did sell everything around March 2009, fifteen years lowest time. I just could not believe that I should learn how to invest from 2000 when I started to invest my 401 K and IRA. 

Double-dip recession, here is the article.