Satvika Thyagam - Explanation.
This is discussed and explained many times in many groups and forums.
To recall it, I am giving it in simple terms?!.

Here in this phrase there are two words:
1. Satvikam - a desiarable attribute
2. Thyagam - giving up (leaving)

We know there are three types fo gunas 1.Satvikam, 2.Rajasam 3.Thamasam and the first one is the best one.

We are knowingly or unknowingly / purposefully or purposelessly always doing actions.
If the action is in the boundary of dharma we get some punyam and when in the boundary of adharma we get phapam.
We must enjoy the fruit of our action, to enjoy the fruits of our karma
repeatedly we are getting birth.
When one understands the truth as "getting birth is worst and attaining moksha is the best" then
he goes to an Acharya and apply for Sharanagathi.

He will continue to do karmas even after getting Sharanagathi.
what will happen for the phalans of those karmas?
Here the acharyan insists his shishyas to do the "Satvika thyagam" after sharanagathi
Every karma consists of three attributes:
1. Karthruthvam - doer(performer) of the karma
2. Mamatha - Owner of the karma
3. Phalan - Beneficiery of the karma
Any one of the above attibute leads to get Rajasa, Thamasa Ahankaras
by leaving those ahankaras (egos) one is getting pure satvika.
How to leave those ahankaras?
By uttering hole heartedly the 'Satvika Thyaga' Mantra before and after every karma
one could leave those ahankaras and he will not affected by the karma.

The Satvika thyaga mantra is the essence of sri Swami Desikan's "Nyasa Dasakam"

'aham mathrakshanabharo mathrakshana phalam thatha
na mama sripaterevaityatmanam nikshibet budha:'

Its wise to realize that 'The reponsibility of protecting myself and the benefit of protection itself
is not mine; Its only of Sriman Narayana'
Read the commentry of Nyasa dasakam given below: