Greed is double edged sword, it could be good or bad depending on the part of sword you are using! Without greed you may not really think wide and far enough for you to achieve greater price for you holding!
I guess we all have to be greedy once in a while to lit the fire on us. To pursue and be aggressive to achieve more. If aiming for more is too much, then that is too much greediness. If we do not control our greediness in trading, the tendency will might lose more to the point that we get broke.