|Chapter 2: Contents of the Gita Summarized|
pratyavayo na vidyate
sv-alpam apy asya dharmasya
trayate mahato bhayat
In this endeavor there is no loss or diminution, and a little advancement on this path can protect one from the most dangerous type of fear.
Krishna here makes a very important distinction between fruitive activities and those performed on the platform of buddhi yoga. The results of fruitive activities is always temporary. One's wealth, knowledge, fame or prosperity are all lost at the time of death. The fruit of one's karma become exhausted as soon as one has enjoyed them.
As said in the previous verse, activities performed on the paltform of buddhi yoga yield no bondages. They alter the consciousness of the living entity, and this effect is permanent. It does not go away at the time of death, and in the next birth one begins from what ever level of advancements made in the previous births.
The "most dangerous type of fear" that Krishna talks about is the fear of gliding down to the lower species of lives, hellish conditions or beng trapped in this samskara-cycle. Srila Prabhupada comments, "Material activities and their results end with the body. But work in Krishna consciousness carries a person again to Krishna consciousness, even after the loss of the body. At least one is sure to have a chance in the next life of being born again as a human being, either in the family of a great cultured brahmana or in a rich aristocratic family that will give one a further chance for elevation. That is the unique quality of work done in Krishna consciousness."
Thus in this verse, Krishna while instructing Arjuna about a higher path also defeats his arguments that he would incur sin by fighting (1.36).
Please read the Sanskrit Verse and the Prabhupada's Purport.