Just a reminder what I wrote back in May and June of this year:
March 2009 To May 2013: The Era Of (More) Cheap Money Could Be Over. Sell Your Stock Winners.
Why chase after the last few percent on the upside? The current Risk/Reward ratio is no longer favorable in most stock markets around the world in my view.
I'm not the only one saying this of course over the past weeks and months, see for example:
One can also predict what will happen to interest rate levels once the FED starts "tapering":
(Source: BoAML. The unwinding of these huge positions may pose many problems of its own, see here.)
PS: Many long-term investors also like to consult the Shiller P/E ratio for answers if the stock market is overvalued at the moment:
Remember that the Shiller P/E ratio has its problems too...
I never would go as far as to call this indicator useless, just be aware of its potential shortcomings outlined in the last link above.