Man is not promised an endless supply of strength for him to store up. Rather, God promises to provide the necessary grace and strength for the present trials.
People in the world are generally quite self-centered. Even saved people are often lovers of their own selves instead of preferring one another.
It has been said that an individual is not truly ready to live for the Lord until he is willing and ready to die for Him. As a believer, one should not fear death.