when a reversal starts it isn t clear whether it is a reversal or a pullback once it is evident it is a reversal the price may have already moved a significant distance resulting in a sizable loss or profit erosion for the trader for this reason trend traders often exit while the price is still moving in their direction that way they don t need to worry about whether the counter trend move is a pullback or reversal 
false signals are also a reality a reversal may occur using an indicator or price action but then the price immediately resumes to move in the prior trending direction again 