2.Insufficient discipline to follow the trading plan

  Second problem why traders lose money is insufficient discipline to follow the trading plan.
  Why wouldn't trader follow the plan? There can be few reasons.
  Maybe he isn't comfortable with his trading plan.
  If you wish to trade 5 different trades on intraday basis, then you don't need long term investment
  strategy. Also, if  you are trying to trade small account size with strategy for large account size then
  you would not feel comfortable.
  Maybe you are trading at a wrong time.
 
   First define your needs and then find trading strategy that will suit your needs.

  Another problem why trader would have insufficient discipline to follow the trading plan is that
  trader doesn't know how  to control the emotions.