[Jainarayan]

The verse is actually

karmaṇy-evādhikāras te mā phaleṣhu kadāchana
mā karma-phala-hetur bhūr mā te saṅgo ’stvakarmaṇi

karmaṇi—in prescribed duties; eva—only; adhikāraḥ—right; te—your; mā—not; phaleṣhu—in the fruits; kadāchana—at any time; mā—never; karma-phala—results of the activities; hetuḥ—cause; bhūḥ—be; mā—not; te—your; saṅgaḥ—attachment; astu—must be; akarmaṇi—in inaction

You have a right to perform your prescribed duties, but you are not entitled to the fruits of your actions. Never consider yourself to be the cause of the results of your activities, nor be attached to inaction.

Do your duty, but do not concern yourself with the results. We have the right to do our duty, but the results are not dependent only upon our efforts. A number of factors come into play in determining the results—our efforts, destiny (our past karmas), the will of God, the efforts of others, the cumulative karmas of the people involved, the place and situation (a matter of luck), etc. Now if we become anxious for results, we will experience anxiety whenever they are not according to our expectations. So Shree Krishna advises Arjun to give up concern for the results and instead focus solely on doing a good job. The fact is that when we are unconcerned about the results, we are able to focus entirely on our efforts, and the result is even better than before. - Swami Mukundananda