Cold and heat, pleasure and pain — these arise when the senses meet the world. They come, and they go. They are not permanent. Endure them, O Bharata. Krishna is pointing at something every person has experienced: seasons change. Winter does not last forever. Summer passes. The chill that makes you shiver today will be a memory next month.
The same is true for emotional experience. The grief Arjuna feels right now — sharp, unbearable, all-consuming — will not remain at this intensity forever. It will shift, soften, transform. That does not mean the grief is fake. It means it is temporary, like every other sensation that depends on circumstances.
The word 'titikshasva' — endure, bear with patience — is not passive. It does not mean 'suffer quietly and do nothing.' It means: understand that this will pass, and do not let a passing sensation derail you from your duty. A farmer does not abandon the field because one season is harsh.