In a survival situation, a willing but unable person is still a tremendous asset. Attitude and worldview are far more important than individual capabilities. Willingness covers absolutely everything. Ability only covers some things. A person who is willing to be of help and service, or do what it takes to keep themselves and others alive, can be invaluable even if they are unable to help in the way they wish they could.
Let me give you an example. Let us say that you are in a firefight and someone who wants to keep fighting gets seriously wounded. They are bleeding from an artery and will die in minutes without emergency help. They want to be whole and strong and stay on their feet in the fight, but they are unable. You rush to their side and drag them behind cover that is not really enough cover for two of you. They are still awake and coherent. What do you do? Do you tell them to lie back and relax and close their eyes? No! You put their weapon (or yours) in their hand and tell them to cover you while you apply a tourniquet and a pressure bandage. As you save their life, you ask them to guard yours and theirs. This allows you to turn your attention from the fight to the casualty while the bullets keep flying. They may be unable to stay on their feet but they are able to stay in the fight.
A person who is willing but unable can still do something to contribute in almost every situation. A bed ridden patient in the hospital can still contribute to the morale of the other patients, medical staff, and visitors by offering encouragement, a good attitude, and a smile. Willingness is an attribute we need to cultivate in ourselves and in others. The act of being willing can overcome the inability that stares you in the face.