What one wants for oneself, one must also desire for others. Islam induces man to share the good things of life with his fellowmen as his brothers. Islam teaches us that the more general a supplication is, the more likelihood there is of its acceptance. There are many sayings of the Prophet, peace be upon him, that corroborate this.
When a Muslim supplicates for others and wishes for them what he wishes for himself, and continues to do so over a long period, he benefits personally. It brings him nearer to Allah as well to his fellowmen. And he gradually attains to a state where his likes and dislikes merge and become one with the pleasure and displeasure of Allah. In addition, he is saved from moral diseases, like malice, envy, spite, and hatred of others. Good and healthy feelings eventually become the hall-mark of his social behaviour, so he is eager to help others and overlook their faults and is ready to forgive them.
"Freedom and Responsibility in Quranic Perspective" - Hasan Al-Anani, pp. 200, 201