Bhagavad Gita Verse 56, Chapter 2

duhkeshvanudvignamanaah sukheshu vigatspruhah |
veetaraagabhayakrodaha sthitadheermuniruchyate || 56 ||
 
One whose mind is not agitated in sorrow, and remains indifferent in joy, and is free from attachment, fear and anger; that contemplative individual is known as a person of steady intellect.
 
duhkeshu : in sorrow
anudvignamanaah : mind is not agitated
sukheshu : in joy
vigatspruhah: indifferent
veetaraagabhayakrodaha : free from attachment, fear and anger
sthitadheeh : person of steady intellect
munih : contemplative person
uchyate : called
 
Shri Krishna continues giving us factors that can destabilize our state of equanimity. In this shloka, he says that the person of steady intellect does not let joy or sorrow upset his equanimity. Now does that mean that the person becomes a stone? No. As long as we are alive, it is natural to experience joy and sorrow. But if we notice that any joyful or sorrowful situation has upset our equanimity for a prolonged period of time, we should be on guard. There usually is an underlying selfish desire at work.
 
For instance, if you know that your favourite dish was planned to be cooked for dinner, but is no longer being cooked because of some reason, you will get disappointed. But if this disappointment persists for a long period of time, it means that you have a deep-seated desire for that dish, which can resurface anytime to cause you further agitation. The goal pointed our in the prior shloka is to free ourselves of as many material desires as possible, and to be "self satisfied with one's self".
 
The second part of the shloka goes deeper into this point by describing how a desire can give rise to fear and anger, both of which cause instability of mind. At the time of writing this, it is the thanksgiving holiday, so it is apt to look at a shopping example. Let's say that you go window shopping and see an ipod that is on sale with a huge discount. Later, you head home but all you can think about is that ipod. That's all it takes - you have developed attachment to it.
 
But that's not all. Right there, you will also develop a fear that it may go out of stock tomorrow, and that you will lose the deal. So you go to the store to buy it the very next day. Now, after a couple of days it stops working. You call the tech support phone number and are kept on hold for 20 minutes. What do you think has arisen in your mind? Anger, of course. And all it took was a desire to take hold of your mind when you saw the ipod. In later shlokas, Shri Krishna gives a more detailed, step by step breakdown of how a simple little thought can bring about one's downfall.
 
In the example, the individual imagined that the Ipod, which is nothing but a material object, would give him happiness. Whereas in reality, there is no happiness "built into" the Ipod. This projection of happiness onto a material object is termed as "shobhana adhyasa".
 
This shloka and the next comprise the answer to the second of Arjuna's four questions, "how does a person of steady wisdom speak?". This shloka is the seed of the first portion of chapter sixteen of the Gita called "daivee sampat" or the qualities of the gods.