In your market analysis, do not get so cerebral that you are ineffective. It doesn’t matter if the computer says so, reality is the last sale. Traders and investors have a tendency to overanalyze. One of the stages every trader (and many investors) goes through is over reliance on mechanical and computerized trading systems. These are very useful tools, but they are not answers. Many times I have seen the technical indicators say, ‘sell,’ yet the market just refuses to cooperate. It keeps trading up. The only truth is the last sale. Fight the tape and you will collapse.
– Dean Lundell, Sun Tzu’s Art of War for Traders and Investors