I feel so guilty but all I can do is cry😞

I have two cats and we took the younger one of the two to get fixed today but she had a really bad inner uterine infection called pyometra. We got her on antibiotics till we could get her fixed but that's all they did was bought us some time. This cat I tell you looked chunky before the infection showed its ugly head but she was a healthy weight, now after having been fixed she looks so skinny where her uterus was. I had no idea how bad it was and I feel so guilty for not getting her fixed sooner. I can't even look at her without crying and it's been like this since we got home 5 hours ago. I think that it triggered my depression in realizing how close I was to loosing another cat before their time. Granted my first cat was brutally murdered, but that's another story. Today had been a pretty ok day before but now all that I can look back on from today is that my cat was suffering for weeks if not longer and there was nothing I could do.