Taking pleasure and pain with equanimity, as though they are one and the same, is the seed for karma yoga. The same applies to gain and loss, victory and defeat, success and failure. Raga and Dvesha - likes and dislikes -are the known causes for our sorrow. There may be a hundred unknown causes, but they can all be reduced to raga & dvesha. Karma yoga was being propounded by Krishna who said, in so many words, 'Don't fight for the sake of raga & dvesha.'
We should not fight just because we do not like someone, nor should we fight just because we like to fight. We need to see the dharma and adharma in fight. Arjuna was fighting dharma yuddha and not out of raga & dvesha. In our works also, we need to see the cause of our work as Dharma Samsthapana and therefore, taking fight as aapad dharma, we should fight it out with the attitude of equanimity.