Let’s say you were given a diagnosis of some type of cancer. It is spreading through your body and the prognosis is very bad. A doctor comes into the room and offers you two pills. The first pill will cure the cancer. The second pill will have an indirect benefit, such as alleviation of some but not all of the pain. The first pill will save your life.
Have you ever seen an employee who was convinced they could not do something; but then they did? It always unleashes a wave of pride and accomplishment. I have seen many an employee who then became very passionate about whatever it was. Suddenly they want to be the best, learn more and get the hit of accomplishment again. The other way people respond is to look outside of the accomplishment and look for other areas.
A mercenary on the battlefield is looking for a reason not to fight. The only thing he gains is his price and in the old days their share of any plunder. A citizen on the other hand is defending his home, family and country. They are fighting for things which are intrinsic to who they are. Once they are on the battlefield, they will fight.