As you know, I do not favor scaling. One of the main reasons is that it lends itself well to emotional interference. I believe that if you feel part of the position should be taken off, then you should take the entire position off. If you feel that some should be left on to run, then all should be left on to run. 
These may sound like contradictory statements to one another, but the trader who is exercising proper positioning sizing and prudent money management will be able to weigh the risks of both sides and generally take the correct one.

These may sound like contradictory statements to one another, but the trader who is exercising proper positioning sizing and prudent money management will be able to weigh the risks of both sides and generally take the correct one.