there is always two possibility the market will move up or down.so when we use for-example moving average and we have placed a buy and suddenly some news came out and the moving average turns to bearish.so most of the traders dont want to accept that they were wrong or market change his decision.they wil wait and hope it to turn back.now the question is why dont you just close your buy position and open a sell position.since the charts and indicators telling you to sell now .