Mark has also posted several interesting pieces on his web-site over the past few weeks including references to "The Four Pillars of Investing" by William Bernstein. Chapter 6 is titled Market Bottoms: The Agony and the Opportunity. It’s only 10 pages and Mark suggests that it is worth the read. In his section titled How to Handle the Panic Bernstein says:
What separates the professional from the amateur are two things: first, the knowledge that brutal bear markets are a fact of life and that there is no way to avoid their effects; and second, that when times get tough, the former stays the course; the latter abandons the blueprints, or, more often than not, has no blueprints at all.
See also Mark's presentation: Should You Be Worried About Your Investments?