I'm so sorry. I know that right now there's nothing I can say to make it any better, but I do understand. I lost two this year and both had the potential to live had we known more and/or not taken our eyes off the mares - even for a couple of minutes sometimes can be too much. After we lost the 2nd foal I looked at our statistics and our success rate is HORRIBLE. At that point I stopped all breeding I was doing for next year! If we have a baby, then it was meant to be, but I'm not breeding any more this year for sure. I may again in the future, but I think I need a break - emotionally - from this for a while.
Again, sorry this happened. Sometimes nothing you do will make a difference. Sometimes you'll beat yourself up thinking it could have. You will never know and beating yourself up isn't going to do anyone any good.