Theancestar says, all these rituals have twofold effects. One, for those with desire, itwill give them what they want. Those without desire, if they perform it, it will give them chita shu, purification. From this comes the entire idea of carma yoga - that same karma which you are performing for worldly success. You fight because it is right and because it will help you in your ultimate goal of spiritual perfection.
Swami Sarvapriyananda teaches the Katha Upanishad, which is one of the most popular Upanishads. The scripture concerns the story of a young man who goes to the house of death to find out what happens after death. The reply describes the nature of reality and the meaning of life.