Upon seeing all the warriors getting crushed by the teeth of Krishna's 𝙑𝙞𝙨𝙝𝙬𝙖𝙧𝙤𝙤𝙥𝙖𝙢, Arjun enquires to know more about who HE really is. Krishna says that HE is the time that is now engaged in wiping out the world and even without Arjun's participation none of them will survive (11.32). He further says that your enemies are killed by ME and you are merely 𝙉𝙞𝙢𝙞𝙩𝙩𝙖-𝙢𝙖𝙩𝙧𝙖 (an instrument in the hands of the Almighty) (11.33). Drona, Bhishma and other warriors have already been slain by ME, don't feel distressed to fight the war (11.34).
The fundamental reason for Arjun's distress is his presumption that he is the 𝙠𝙖𝙧𝙩𝙝𝙖 (doer) or the killer in the present context. This is aham 𝙠𝙖𝙧𝙩𝙝𝙖 (I am a doer) or 𝙖𝒉𝙖𝒏𝙠𝒂𝙖𝒓. He tries to justify this by saying that killing his teachers and relatives for the sake of the kingdom is not good. Krishna breaks Arjun's illusion by showing him a glimpse of the future where all warriors are entering the mouth of death. Krishna clarifies that even without Arjun's participation none of them will survive and Arjun is just a 𝙉𝙞𝙢𝙞𝙩𝙩𝙖-𝙢𝙖𝙩𝙧𝙖.
𝘼𝒉𝙖𝒏𝙠𝒂𝙖𝒓 tells us that we are performers, achievers, knowers etc. It also presumes others to be so. This results in expectations from ourselves and others which finally leads to misery. Being 𝙉𝙞𝙢𝙞𝙩𝙩𝙖-𝙢𝙖𝙩𝙧𝙖 is the complete opposite of this.
Krishna used many words for the Eternal State like Ever Content; 𝑽𝙚𝒆𝙩 𝙍𝒂𝙖𝒈 which is beyond 𝙍𝒂𝙖𝒈 and 𝙑𝙞𝙧𝙖𝙖𝙜; 𝘼𝙣𝙖𝙖𝙨𝙖𝙠𝙩𝙞 which is beyond 𝘼𝙖𝙨𝙖𝙠𝙩𝙞 and 𝙑𝙞𝙧𝙖𝙠𝙩𝙞; Doing 𝙆𝙖𝙧𝙢𝙖 without expecting 𝙆𝙖𝙧𝙢𝙖𝙥𝙝𝙖𝙡. 𝙉𝙞𝙢𝙞𝙩𝙩𝙖-𝙢𝙖𝙩𝙧𝙖 is another word for the same Eternal State of joy.
If Bhagavad Gita can be described in one word, it is 𝙉𝙞𝙢𝙞𝙩𝙩𝙖-𝙢𝙖𝙩𝙧𝙖. The journey of Gita is from 𝙖𝒉𝙖𝒏𝙠𝒂𝙖𝒓 (𝙎𝙖𝙣𝙜𝙝𝙖𝙧𝙨𝙝) to 𝙉𝙞𝙢𝙞𝙩𝙩𝙖-𝙢𝙖𝙩𝙧𝙖 (𝙎𝙖𝙢𝙖𝙧𝙥𝙖𝙣). Nothing remains serious, tense or fearful when 𝙉𝙞𝙢𝙞𝙩𝙩𝙖-𝙢𝙖𝙩𝙧𝙖 is inculcated at deeper levels.