Yu gi oh help pls answer!?!?!?!?!?!?!?!?!?!?!?!?…

alright me and my cousin have been arguing against wat works. say he attacks me and i use enchanted javelin(which says precisely when your opponents monster attacks. increase your life points by the attacking monsters attack. ya he agrees with me that i get life points but he says that that my monster is destroyed and still take away life points which is totally stupid thatn whats the point of it wouldnt it just be a negate attack!