How do I make it to if I attack a mob, my main-hand item gains durability?

I'm experimenting because its my first time with anything like this, but I cant seem to get it right, it always targets the things I want to kill and not myself, I have the blocks that let my weapon's durability go up, but it never targets the player, I'm getting a bit frustrated but its still fun to mess with, think I can get some help here?

(I would show you what the blocks look like, but I change them so often I cant tell what was the original)