BRAHMASTRA

You find a lot of difference in Arjuna and Ashwathama. Arjuna was the disciple of Dhrona and Ashwathama his Son. Both were good fighters. Arjuna was a straight fighter followed all rules whereas Ashwathama hid his face and attacked the innocent ones from behind in darkness while they were on sleep.  Even at the end of Kurukshetra war he sent his Brahmastra to kill the foetus  of Uttara and Lord Krishna saved her from the misery and taught him that arrows especially Brahmastra are not supposed to be aimed at the innocent ones. It is justified that Ashwathama was angry on Pandavas for killing his father and the situation in which that happened would have raged his anger. He could have fought a straight war instead of killing the innocent ones on their sleep from behind. And about the maturity of Arjun was such that he did not wage a war but only fought back when Kouravas followed the heinous method of finishing  Pandavas and denied of their  rights. Kouravas believed in power based war and Arjuna believed in a chariot Krishna had led for him.

There you find the difference between Arjuna and Ashwathama. Arrows should be used for good cause and not as a sting tool to finish of innocent ones or to silence and isolate your opponet.. Arrows used for a good cause will give you good result and when used to tarnish innocent ones for sure will come back to you..