I agree it's important that to build fighting ability, you regularly get hit for all the reasons you say. The ability to not lose your head when you get punched right in the face is really important, and can't be taught without actually getting punched right in the face. But I don't agree that every single drill you do, you need to get hit. There are certain drills we do where I'm trying to train something specific, and being hit in the face a lot would not enhance that particular drill. In those situations, I pull each shot before it lands. But on Monday night sparring nights we hit and get hit tons, and if I don't see a punch coming, I eat it.