You definitely don't need to 'toughen up' your nipples. If you think about it 'toughening up' leads to harder nipples not hardier nipples so they are more likely to crack and bleed than normal nipples that are soft and more flexible.
I also agree with Amber. I had quite a bit of pain that only settled down after about 3 months despite good attachment (and yep I am positive the attachment was good). I am sure I did quite a bit of damage myself actually because when I was told by one midwife that if it was painful then the attachment wasn't good enough which led to me constantly detaching and re-attaching bub. Only to discover later that the attachment was just fine. So I guess as Barb said education is the key and try not to worry about all of the differing opinions that you are likely to get in hospital from each different midwife.