Most people who have little knowledge of Bhagavad-gita call themselves follower of Karma Yoga. When discussed about it, they cite this famous verse from Bhagavad Gita (2.47):
karmany evadhikaras te
ma phalesu kadacana
ma karma-phala-hetur bhur
ma re sango'stv akarmani
General understanding, which people hold, about this verse is that we should work hard without worrying much about the result. This understanding gives an inspiration to continue working hard even in times of failure. But it is not complete or actual understanding of the Sloka. The exact English translation of the sloka is, "You have a right to perform your prescribed duty, but you are not entitled to the fruits of action. Never consider yourself the cause of the results of your activities, and never be attached to not doing your duty."
We cannot sit idly even for a moment as it is stated in Bhagavad-gita 3.5, "na hi kaschit ksanam api jatu tisthaty akarma-krt". So first part of this sloka (Bg 2.47) tells us to do our prescribed duties. And while performing the duties we should not consider ourselves the cause and the enjoyer of the fruits of action. It is not very difficult to understand that we are not the only cause of results of our activities. Because many times we do not get desired result from our activity despite putting our best endeavor. The difficulty is to not consider ourselves the only enjoyer. In fact, we will lose enthusiasm to perform an activity if we are not to enjoy the result. For example, if government levies heavy tax on extra earning then citizens would not be inspired to earn more. But second part of the sloka asks not to lose enthusiasm to do our duty.
Now the question arises, “if I have to work and not enjoy the result then who is the enjoyer of the result of my work?” This has been answered in Bhagavad Gita 3.9: "yajnarthat karmano". The result of our action should be distributed to everyone through the central point of God (Yajna). We can keep the portion of the result as per our requirement and rest has to be offered to God and he distributes it to everyone. Just like Government realizes taxes from us and distributes it to everyone in the form of various facilities. The next question is how can I give the result of my activities to God? We can give the result of our activities to God by contributing it to the mission of God. And what is the mission of God? That is stated in Bhagavad Gita 4.7-8. God's mission is to remind people of their relationship with Him, which they have forgotten in contact with material world.
One may ask, "Why should I not enjoy alone the results of my activities?” The answer is, it is not possible to enjoy alone the results. We are very limited and results of activities are also very limited. We will never feel satisfied by trying to enjoy alone the results. We will always feel incomplete and keep trying to expand the results. But when we contribute results to God who is unlimited and complete, in his association we will be able to enjoy it to our satisfaction. Also, we are not the only cause of the results. Actual cause is God as mentioned in eighteenth chapter of Bhagavad Gita and we are just partial cause. So actual enjoyer of results of our activities is God and we are just partial enjoyer.
Thus the complete understanding of the sloka under discussion is that: we should perform our duties without considering ourselves the whole cause and enjoyer of the results. We are partial cause and partial enjoyer. The full cause and full enjoyer of results our activities is God. Acting under this principle is called Karma Yoga. And by practicing Karma Yoga we will not be affected by good or bad results and success or failure of our activities. Thus we will be fully Happy, Peaceful and Satisfied.