It seems when just about everyone is positive on the market ( whatever market i.e. equities, real estate, gold, silver, etc.) the top of that market is at hand. Why? Everyone is in and who is left to buy?
A study was once done of a very popular mutual fund. It found over a 10 year period the fund did around 12%. The average investor in the fund did 4% over the same period. Why? There was a lot of money coming into the fund near its high and a lot leaving the fund near its low.