In short, don't ever ever ever take my investment advice. However, I will note that when I tongue-in-cheek called the market top on May 27, the S&P closed at 2123 and has not closed higher than 2128 since.
The reason market timing is virtually impossible is because the actual timing can be so skewed . You can be sure the market is overvalued but it can take years for that to play out, particularly when governments (e.g. US, China) are pumping liquidity into the markets to keep them afloat.
A good example is China. I (and many other much smarter people) were recognizing the China market was overvalued years ago, but had one shorted the China market back then you would have been short-squeezed into oblivion before the actual crash came about this year.
While fundamental investing isn't worthless, the effects of fundamentals seem to get easily swamped by government actions, such that predicting government actions is far more important to investment success than figuring out corporate fundamentals. I learned to tear apart company financials from one of the best back at HBS, but I have no ability to figure out when the Fed will or will not stop dumping money into the markets. So I buy a few index funds and try not to look at them too much.