Bhagwad Gita in Chapter-2 Verse-46,47 says ...
You have a right to perform your prescribed duty, But you are not entitled to the fruits of action. Never consider yourself to be the cause of the results of your activities, and never be attached to not doing your duty.
O Dhananjay (Winner of Wealth), perform action, abandoning attachment, beaing steadfast in yog, and balanced is success and failure. Evenness of mind is called Yog.
My question is How can we perform actions without expecting results, when it's the result who will decide our fate?
I think what Gita is trying to say here is that, keep yourself balanced in both success and failure. Because in both situation you might get distracted from path of your duty. In case of extreme joy and happiness of success, You might think that you have achieved a lot and stop expanding your knowledge. Which will ultimately lead you towards the disaster. In case of failure, By feeling sorry about it and not doing anything. Still you are not doing fruitful work and again you are moving towards the path of your disaster.
But How can a person get over with this feeling of success and failure without expecting results of its action becasue its the result that decide the fate. For a student how can he give the exam and do not expect anything from its result, When its the result who will decide his future. Does Gita here trying to say that, You Perform your actions and forget about the results. Take decision after getting results and move on quickly.
What kind of attitude a person should build so that he can get away himself from the feeling of success and failure. And Be happy in the both situations?