Bhagavad Gita Verse 41, Chapter 2

vyavasaayaatmikaa buddhirekeha kurunandana |
bahushaakhaa hyanantaashcha budhyovyavasaayinaam || 41 ||
 
Here, the thoughts of the determined are focused, O Kurunandana. The thoughts of the irresolute are many-branched and infinite.
 
vyavasaayaatmikaa : determined
buddhihi : thoughts
ekaa : focused
iha : here
kurunandana : O Kurunandana
bahushaakhaa : many branches
hi : consists of
anantaaha : infinite
cha : and
budhyaha : thoughts
avyavasaayinaam : irresolute
 
From this shloka onwards, Shri Krishna began to provide Arjuna with a practical "toolkit" of techniques that would enable him to conduct his svadharma with equanimity of mind. This shloka explains the first technique in this toolkit: maintaining constant focus on the goal prescribed in the Gita teaching.
 
The goal mentioned in a prior shloka is clear to all of us : equanimity of mind in any situation. So the very first thing that Shri Krishna instructs us to make a promise to ourselves that "I will only focus on one desire - that of maintaining equanimity. If it has nothing to do with my svadharma, I will not entertain that desire."
 
Consider an example. When Mr X visits the grocery store with a shopping list, he quickly and efficiently gets the items on the list and leaves the store. He is focused on acquiring the objects in his shopping list. But when he visits the mall or an electronics store, his mind starts entertaining "many-branched and infinite thoughts" e.g : "Oh look at this new IPod", "Can I get it cheaper here?", "When's the new HDTV coming out" etc. and eventually ends up spending over 3 hours in the mall. Therefore, focus is extremely important in any endeavour.
 
Now, let's assume we focus on the one desire to maintain equanimity. How do we know whether we are on the right track? To that end, this shloka very beautifully gives us a "checklist" so that we can keep tabs on our focus. At some point every day, preferably at the end of the day, we should ask ourselves two questions and write down the answers in a journal:
 
1. What objects/people/situations did I keep obsessing about today?
2. How many of these obsessive thoughts did I have?
 
If we notice over time that the quantity of our obsessive thinking has begun to diminish, it means that our intellect is beginning to focus on the ultimate goal of the Gita teaching.