Bhagavad Gita Verse 37, Chapter 3

Shree Bhagavaan uvaacha:
kaama esha krodha esha rajogunasamudhbhavaha |
mahaashano mahaapaapmaa viddhyenamiha vairinam || 37 ||
 
Shree Bhagavaan said:
It is desire, it is anger, born of rajas. It is a voracious eater, a great sinner. Know it to be the enemy (here in this world).
 
kaamah : desire
eshah : this
krodha : anger
esha : this
rajoguna : rajas
samudhbhavaha : originated from
mahaashanah : voracious eater
mahaapaapmaa : massive sinner
viddhi : know
enam : it
iha : in this
vairinam : enemy
 
Earlier, Shri Krishna had mentioned that likes and dislikes are like highway robbers. They distract us from our path. But now, he uses the term "enemy" to refer to desire. What is the difference between a highway robber and an enemy? A highway robber does not care who we are, he just wants to distract us, rob us and let us go. But an enemy knows us, knows our weaknesses well, and intends to cause us great harm. Therefore, desire and anger are much more dangerous than likes and dislikes.
 
When we give a lot of attention to our likes and dislikes, it increases the proportion of the active quality, or rajas, in our system. When this happens, our likes and dislikes grow in size like weeds and become strong desires. We then go into a vicious cycle : strong desires create more rajas, which in turn makes the desires even stronger. Similarly, if dislikes grow, they turn into anger and hatred.
 
Now, when a strong desire gets fulfilled, there is a temporary pause in that desire, and the mind becomes still for a short amount of time. As we have seen earlier, an absence of desires clears the mind and lets the eternal essence shine through. When that happens, we experience peace and happiness. But, most of us wrongfully attribute that temporary spark of happiness to the object we just acquired, rather than to the absence of desire. So then, we go through life fueling our desires, in the hope that we can recreate that experience.
 
The tendency to recreate happiness through repetitive acquisition of an object is called greed. Moreover, the ego becomes strong through the increase in rajas, and it begins to go outward, comparing us with others. If someone has less than us, pride is created. Conversely, if someone has more than us, jealously is created.
 
The practical lesson here is that we should not encourage our likes and dislikes. In other words, if a like or dislike arises in the mind, we should not give it too much attention. If we do, it will get stronger. It is easier to control a like or a dislike. Once it has grown into a strong desire or hatred, then it becomes much difficult to control.