The entire content of this mail is from Shri V N Gopala Desikan's Srimad Bhagavad Gita, published by Vishishtadvaita Research Centre, Chennai and The Bhagavad Gita by Swami Chidbhavananda published by Ramakrishna Mission
Tyaga of sattvika nature is indispensable 9-12
1 Gita Sloka Every Day - Chapter 18 - Moksha Sanyasa Yoga - Sloka 9
Karyam iti eva yat karma niyatam tam kriyate arjun I
Sangam tyaktva phalam cha eva sah tyagah sattvikah matah II sloka 9
कार्यं इति एव यत् कर्म नियतं तम् क्रियते अर्जुन I
संगम त्यक्त्वा फलम् च एव सः त्यागः सात्त्विकः मतः II श्लोक 9
Whatever obligatory work is done, O Arjuna, merely because it ought to be done, abandoning attachment and also fruit, that abandonment is deemd to be sattvika.
Shri V N Gopala Desikan's Srimad Bhagavad Gita
When the compulsory karmas, ie. the nitya and naimittyika karmas and the panch amaha yagnas, which are laid down in shastras, according to one's caste and asrama; are done as a matter of duty, for the pleasure of the Lord; as a form of worship of Myself, the Lord; giving up the thought that he is the doer; giving up one's sense of possession in the karmas; without desiring the fruits of such karmass; such a tyaga is called as sattvika tyaga.
The sattva quality produces knowledge of things; as they really are; and thus the correct meaning of sastras is known. All works are therefore, performed with sattvika tyaga.
The Bhagavad Gita by Swami Chidbhavananda
The very performance of karma is abandoned both in the tamasika and rajasika tyagas. But such a suspension of work does not take place in the sattvika tyaga. The execution of duty goes on unabated. All karmas, including the nitya karma are fruit bearing in nature. But the sattvika tyagi is not concerned with the fruit; he does his duty to the best of his ability though he is unattached to it. He does not renounce karma; he only renounces the agency. Calmness and purity are born of this frame of mind.
The inpatient in the hospital has no intention to be there permanently; neither does he want to be treated all through his life. Still he willingly undergoes the treatment with an attitude of detachment. Such a man as he is the one who truly renounces ailment. The sattvika tyagi renounces teh fruit of his action just like the sensible patient who seeks to be rid of all his ailments
The patient however, abhors his disease. the sattvika tyagi is devoted to his obligatory duty. Breathing is the obligatory duty of all living beings. The yogi resorts to pranayama or the scientific way of breathing which yields great benefits. Still, the yogi does not do this great act with any atatchment; he does it as disnterestedly as others do their normal breathing. He is verily a healthy man who is free from body consciousness while being in the body. This yogi is free from the sense of agency while engaging himself in work intensively. Adoring the Lord, serving the society, meditating on the supreme - all these spiritual activities go on vehemently. But the sadhaka is not conscious that he is the doer of these benign duties. His renunciation is the sattvika tyaga