A core theme of the Bhagavad-gita is that in our words, thoughts, and especially our actions, we should be content with our intent and doing the best we can. From a spiritual perspective that is the success. If we are really doing the right thing in the right way, that is going to nourish ourselves and help others with the right purpose. This in itself is our success. The results we have no control over, but we do have control over the choices we make and the intentions that we have.
So, yoga really means to make choices and to cultivate intentions and purposes that are wholesome and healthy for our wellbeing, for the wellbeing of the environment and for the wellbeing of other people. And we should be grateful just for that opportunity. Just the action itself, just the motive itself is our success – whatever the results may be. In this consciousness our joy and fulfillment is transcendental to the apparent actions and reactions of this world.
In the Bhagavad-gita, Arjuna was taught that whether you win or lose is not important. Honor/dishonor, happiness/ distress, success/failure, health/disease, life/death… all of these dualities are always playing with each other in this world, and we have some degree of control over the situation, but not much. Yoga is not about what the result is, but your motivation and how you do it. If we are happy with that, then our happiness is something very deep, and the circumstances and people in this world cannot meddle with it. —Radhanath Swami