This Bhagavad Gita quote stands out the most, showing us a simple and effective way of fighting any battle. While Lord Krishna may have been referring to the situation in the Kurukshetra battle, trying to convince Arjuna to fight with all of his might. The teachings from this Bhagavad Gita quote can be applied to any situation, the world around us is made in such a way that nothing is earned without any struggle, every situation is nothing but a battle with the existing forces.
Indeed, when you are truly impervious to the external things you are in a much better position to deal with any situation. So let yourself be the same state of mind, be it a joy, sorrow or excitement. You can express excitement, sadness or grief, but deep down you should be strong like a rock. You can find other inferences of this Bhagavad Gita quote in Hindi on this site.
Source: Bhagavad Gita Quote 2.38
सुखदुःखे समे कृत्वा लाभालाभौ जयाजयौ।
ततो युद्धाय युज्यस्व नैवं पापमवाप्स्यसि॥
sukhaduḥkhe same kṛtvā lābhālābhau jayājayau।
tato yuddhāya yujyasva naivaṃ pāpamavāpsyasi॥
Fight for the sake of duty, treating alike happiness and distress, loss and gain, victory and defeat.
Fulfilling your responsibility in this way, you will never incur sin.
जयपराजय लाभहानि और सुखदुःखको समान करके फिर युद्धमें लग जा।
इस प्रकार युद्ध करनेसे तू पापको प्राप्त नहीं होगा।
Read other Bhagavad Gita quotes here.