Zombies are dead. They don't feel, they don't get hurt, and they don't ever stop. I can't think of anything that has killed more people than the virus itself than people fighting zombies and forgetting they're dead. One guy bought it because he was in the middle of killing a zombie when he dropped his weapon. Like a damn fool he punched the Z in the face, expecting it to fall back like a living person would. Z just walked through the punch and bit him on the face.
I remember one time Sarah was training some women on takedown techniques, and one timid little thing tried really hard, but she kept holding back when it came to incapacitating the enemy. Sarah asked why and the woman replied she wanted to kill the zombies, but she didn't want to hurt them.
The big takeaway here is zombies don't feel anything. No emotions, no feelings, no pain, no nothing. They will not stop until stopped. You have to get it out of your head that they will be knocked unconscious, that they will retreat after you cut their arms off, or they will run from superior numbers. They don't think, and they never will. They are pure instinct, wrapped up in a rotting corpse of a body.
If you think of them in any other way, you will be one of them in short order.