In plain words
You must do all actions to please God. The one who held out such an ideal is Bhīṣmācārya. He strove solely for the contentment of the Ātma; he bowed to his mother's command and became worthy of her love.
In the battle, the arrows Arjuna shot stuck fast all over Bhīṣma's body. Bhīṣma too shot arrows. But they struck Śrī Kṛṣṇa, who was blameless. Kṛṣṇa's whole body was soaked in blood. Many things happen in a war. There, there is room only for victory and defeat; there is no room for weighing what is good and what is bad. Bhīṣma lay on a bed of arrows for 56 days, waiting for the holy time of Uttarāyaṇa. In all those days he did not drink even a drop of water. At his last hour he called Arjuna, said he was thirsty, and asked him to bring his mother Gaṅgā just once and quench his thirst. Before giving up his life, he hoped to receive his mother's love and grace. Arjuna took an arrow and struck the ground beside Bhīṣma's head. At once Gaṅgā shot up from the earth with a rush and fell into Bhīṣma's mouth. Today many take the name ‘Arjuna’, but do they act as the name asks? Arjuna means one whose citta is pure. To him belong “Arjuna, Phalguna, Pārtha, Kirīṭi, Śvetavāhana, Bībhatsa, Vijaya, Kṛṣṇa, Savyasāci, Dhanañjaya...” and many other such titles.
In the holy place of Śrīśailam, Bhramarāmbā and Mallikārjuna sit enthroned. Who is meant by Mallikārjuna? Mallikā = like the jasmine flower, arjuna = the white one: that is the meaning. Bhramara means a bee. From the joining of the words mallikā and bhramara, you must understand that this God is the jasmine flower spreading its fragrance, and that the Goddess is the bee that enters that flower and drinks its nectar, and that she is a symbol of true Bhakti.
Among the Pāṇḍavas, Arjuna was very great. He was not one to loose an arrow at anyone needlessly.