42. The verse has been taken from the Kathopanisad which gives the hierarchy of desires. The pecking order is on the basis of subtlety, pervasiveness and control.
The senses are great as they have a powerful attraction to the world. The mind is more potent. When tragedy strikes you lose your appetite. The intellect is even more influential. The mind submits to intellectual conviction. And Atman is the strongest. All desires fade away under the sway of Atman.
So if you want to conquer desire move up from physical to emotional, intellectual, and finally to spiritual desire. The lower desires will not bother you but the objects of desire will come to you effortlessly!
43. There are two ways of dealing with desire – Knowledge of the higher and self control. In order to gain knowledge you must refrain from the world for a while. The more knowledge you gain the more you are able to control yourself. With more restraint you gain more knowledge.
If there is only control it leads to frustration. Mere knowledge gets washed away with indulgence.
The chapter ends on a highly inspiring note. Krsna addresses Arjuna as Mahabaho, mighty-armed, to remind him of his original stature. Then He asks him to kill the enemy in the form of desire. A warrior tends to react to this approach. He then provokes Arjuna by saying desire is very difficult to conquer.
Thus Karma Yoga is the method of overcoming desire by dedicated action towards a larger cause in the field of your svadharma.