Please don't beat yourself up over an egg that pipped and did not hatch. Many times there is something wrong with the chick and it would most likely have died anyway. Most times there is nothing you could have done to save it. Better to have them pass in the shell than to hatch have to be put down due to deformities or other internal fatalities we can't see.
It hurts every time it happens. You never get used to it. :aww
I use to. Especially with the first ones. I hate it when they fully develop and never get the chance to break free of their egg. Just something about it kills me. I still haven't gotten cold to it yet, I still sigh and get a distaste in my mouth.
I did shed a few tears over my peafowl eggs I tried to hatch a few weeks ago. I had one peachick become fully developed and was even rock the egg. He never pipped and died in the egg before I could intervene. The real kicker was that it was something I could have prevented, the humidity was too low apparently.
My solution, is not to overthink it. Do not ask "What if" or "If only"s. Just swallow the emotion and go bury it.