In the final verse of the Bhagavad Gita, we are reminded of the previous verses important points. Arjuna asks what true sannyasa (renunciation) is. Krishna replies that renunciation of selfish actions and even renunciation of the fruits of actions is the brings true freedom. We continue to act, as has been pointed out throughout the Gita, but we give up the desire for a particular outcome or a particular reward for our actions. We act simply because it is our duty. Egoism, selfishness and attachment are all possible when we act; so it is renunciation of all of these that we should be focused on.
When we perform action with a mind toward sacrifice, gift and austerity it’s still possible to get caught up in the reward of it; whether a pat on the back, a pay raise or an award. When we act only from the place of giving, with no expectations, we are purifying our souls according to the Gita.
We are reminded that our actions may be sattvic, rajasic or tamasic in these lines:
20. That by which one sees the one indestructible Reality in all beings, not separate in all the separate beings—know thou that knowledge to be Sattwic (pure).
21. But that knowledge which sees in all beings various entities of distinct kinds as different from one another—know thou that knowledge to be Rajasic (passionate).
22. But that which clings to one single effect as if it were the whole, without reason, without foundation in Truth, and trivial—that is declared to be Tamasic (dark).