Yagna symbolises sacrifice or selfless actions. In this context, Krishna says (4.25), "Some yogis perform sacrifices to gods; others perform sacrifice by offering sacrifice itself in the fire of Brahman (Supreme God)."
For one living without awareness, living is just gathering and preserving. The next higher stage of living is sacrificing things, thoughts and feelings. It's like sacrificing the seeds of ahankaar (I am doer) into the fire rather than letting them multiply on the fertile soil of the mind. The third stage is sacrificing the sacrifice itself realising that all of them are Brahman.
It can be said that the mind oriented karma yogi keeps looking for action and doing sacrifice is the path for him. The intellect oriented gyan yogi is about pure awareness and he sacrifices the sacrifice itself. While the former is sequential, the latter is an exponential or quantum jump, but rare. However, both paths lead to the same destination.
Krishna explains this reality in the context of senses and says that "Certain devotees offer as oblations in the fire of inner control, their powers of hearing and other senses. Others offer sound and other sense objects as sacrifice in the fire of senses (4.26)." In essence, the paths of sacrifice and sacrificing the sacrifice.
Krishna explains the relationship between senses and sense objects many times. The prominent explanation is, "Sense organs naturally experience raag (fondness) and dwesh (aversion) for their respective sense objects; one should be aware of this duality (3.34)."
Through specific effort, the karma yogi breaks the bridge between the senses and sense objects which is the sacrifice mentioned in the first part. The second part is for a gyan yogi who sacrifices the entire process to be just a sakshi through awareness. In both situations, the destination is transcending the polarities.
Source - Daily World