Well, history has shown that you can lose most of the major, pitched battles but still win the war:
http://en.wikipedia.org/wiki/Vietnam_War
As long as the Taliban/ Al Queda are throwing themselves at coalition troops, ISAF soldiers will die. As long as ISAF soldiers die without any real signs of progress, public support for the war will erode, followed by an erosion of soldiers' confidence in their mission and leadership. If things get that bad in Afghanistan, a Vietnam-style pull out will probably occur. If that happens, the Taliban effectively won, no matter how many battles they lost.
What the coalition forces need is a Patton-style general who will always press the attack, blow

up, kill people, and not worry about the political ramifications.
When will the military learn that prolonged war results in low confidence and low support? When will they learn that all the Taliban have to do is wait us out?
We need to attack and kill every last one of them.