The spirit is the cause of all our thoughts and body-action, and everything, but it is untouched by good or evil, pleasure or pain, heat of cold, and all the dualism of nature, although it lends its light to everything.
Take up one idea. Make that one idea your life - think of it, dream of it, live on that idea. Let the brain, muscles, nerves, every part of your body, be full of that idea, and just leave every other idea alone. This is the way to success.
For a warrior, nothing is higher than a war against evil. The warrior confronted with such a war should be pleased, Arjuna, for it comes as an open gate to heaven. But if you do not participate in this battle against evil, you will incur sin, violating your dharma and your honor.