Bhagavad Gita Verse 27, Chapter 17

yajnye tapasi daane cha sthitihi saditi chochyate |
karma chaiva tadartheeyam sadityevaabhidheeyate || 27 ||
 
Steadfastness in sacrifice, austerity and charity is called Sat, and also, action relation to these is called Sat.
 
yajnye : sacrifice
tapasi : penance
daane : in charity
cha : and
sthitihi : steadfastness
sat : Sat
iti : in this manner
cha : and
uchyate : is called
karma : action
cha : and
eva : also
tadartheeyam : related to these
sat : Sat
iti : in this manner
eva : also
abhidheeyate : is called
 
In the concluding shlokas of this chapter, Shri Krishna described the purifying chant Om Tat Sat. Any sattvic action will be freed of defects, attachment to the action and its reward will be weakened, all notions of duality will be muted when we use this purifying chant. Now we may say that in this day and age, we may not have the time to follow the guidelines given in this chapter to make our actions and our intake sattvic. Following the guidelines in the scriptures is beyond our scope anyway.
 
As usual, Shri Krishna makes things easy for us. He says our stithi, our steadfastness is towards Ishvara, is the most important thing to pay attention to. If we take care of our steadfastness, and chant Om Tat Sat with that steadfastness, every action that we perform will become sattvic and a means towards liberation. What does sthithi or steadfastness mean? It is that which our mind is occupied the most. If we keep a notebook next to our bed, and write down the first thought that comes to mind when we wake up, we will know what our stithi is within a few days.
 
Many people say that a sport such as cricket or tennis is their life. Others say that it is their career, others say it is their family, others say it is their family and so on. It is the first thought that they wake up with in the morning. When our first thought, and also, the constant background thought throughout the day is that of Ishvara, all our actions will automatically become sattvic. We will not have to take any additional precaution or follow any other guideline. For instance, if we are in constant thought of Ishvara, we will never think of donating anything with a view to get something back in return. Action follows thought, and with the constant thought of Ishvara, actions take care of themselves.