The enderman will stop targeting you after you hit it around 2-3 times. They will also teleport far from the player and become neutral so they do not return to fight the player. Meaning their enderpearls cannot be collected once they teleport far away and go neutral. This has been rather annoying for me and my friends grinding enderpearls. Every time we attack an enderman either in the nether, or over world, they teleport somewhere far and stop being hostile. Meaning we can not find them and finish them off for their pearls. They do not even teleport a few blocks away, they teleport all the way across from you. Meaning they become almost impossible to locate.