I believe that just as you wait for the market to move in a certain way (via indicators) you should exit the same way.
to be exact, let the market take you out. either via a SL for a loss, or a trailing stop loss for a profit.
Of course this only works for bigger pip trades, as scalping would not work with this situation.
however if you are entering a trend trade, let it breath, when your up 30 pips, move to BE+2, and then trail at 35 pips... this way your not too close so you let the trade float the waves, and yet you let the market decide how much you make, why close out after 50 pips if the market is going to give you 100???