Analysts need to test trading systems and technical analysis indicators on a wide array of data in different types of trading markets. Additionally, many traders and analysts don't forward test their trading systems and technical analysis indicators in real time. Thus, they are trading on not a sound, valid basis. Many traders fail to incorporate sound risk management techniques in their trading systems. Additionally, many traders fail to incorporate stop loss orders with their initial orders when using technical analysis indicators only.
Traders also tend to over-optimize their trading systems.
They are always trying to trade with the parameters which generate the highest amount of wins. However, in real time these over-optimized systems rarely perform well. Another trap traders fall into is to use too many technical analysis indicators. Find the few that work consistently well for you and go with them. I find the time tested technical analysis indicators to be the best.