The Lord says in Bhagavad-gītā (15.15):
sarvasya cāhaṁ hṛdi sanniviṣṭo
mattaḥ smṛtir jñānam apohanaṁ ca
“I am seated in everyone’s heart, and from Me come remembrance, knowledge and forgetfulness.” When two parties fight, the fighting actually goes on under the direction of the Supreme Personality of Godhead, who is Paramātmā, the Supersoul. Elsewhere in the Gītā (3.27) the Lord says:
prakṛteḥ kriyamāṇāni
guṇaiḥ karmāṇi sarvaśaḥ
ahaṅkāra-vimūḍhātmā
kartāham iti manyate
“The bewildered spirit soul, under the influence of the three modes of material nature, thinks himself the doer of activities that are in actuality carried out by nature.” The living entities work only under the direction of the Supreme Lord. The Lord gives orders to material nature, and she arranges facilities for the living entities. The living entities are not independent, although they foolishly think themselves the doers (kartā).
Victory is always with the Supreme Personality of Godhead. As for the subordinate living entities, they fight under the arrangement of the Supreme Personality of Godhead. Victory or defeat is not actually theirs; it is an arrangement by the Lord through the agency of material nature. Pride in victory, or moroseness in defeat, is useless. One should fully depend on the Supreme Personality of Godhead, who is responsible for the victory and defeat of all living entities. The Lord advises, niyataṁ kuru karma tvaṁ karma jyāyo hy akarmaṇaḥ: “Perform your prescribed duty, for action is better than inaction.” The living entity is ordered to act according to his position. Victory or defeat depends on the Supreme Lord. Karmaṇy evādhikāras te mā phaleṣu kadācana: “You have a right to perform your prescribed duty, but you are not entitled to the fruits of actions.” One must act sincerely, according to his position. Victory or defeat depends on the Lord.
Vṛtrāsura encouraged Indra, saying, “Don’t be morose because of my victory. There is no need to stop fighting. Instead, you should go on with your duty. When Kṛṣṇa desires, you will certainly be victorious.” This verse is very instructive for sincere workers in the Kṛṣṇa consciousness movement. We should not be jubilant in victory or morose in defeat. We should make a sincere effort to implement the will of Kṛṣṇa, or Śrī Caitanya Mahāprabhu, and we should not be concerned with victory and defeat. Our only duty is to work sincerely, so that our activities may be recognized by Kṛṣṇa.
Srimad Bhagavatam 6.12.7 purport