How to fight?

How to fight ( i.e. Engage with external world) and always win: become indifferent to either outcome or see good in either outcome.

Same point is there in the Bhagavad GItA:

हतो वा प्राप्स्यसि स्वर्गं जित्वा वा भोक्ष्यसे महीं

hato vA prApsyasi svargam  jitvA vA bhokshyase mahIm.

Dying in battle you will attain Heaven or winning you will enjoy the World.

This yoga resulting from vicAra leads to invincibility, fearlessness and absence of sorrow. Fear and sorrow only apply to pleasing or unpleasing experiences of the senses and the ego; they do not pertain to the real Self. The changeability of mind's attitude towards same object ranges from rAga (attraction) to dvesha (revulsion). Resorting to the Self one transcends both.