Sorry to hear about this as well.
Unfortunately - accidents are accidents, and we can't always control life as much as we want to.
Sometimes I think it helps to turn a bad experience into a good one to deal with the fear and guilt. In other words, try to do a good deed. Sometimes in these situations, you think "why did this have to happen? What was the reason?"
If you try to turn it into a good deed (volunteering at a rescue, adopting a shelter animal, helping with a TNR program), then it helps you reconcile, "OK. This happened. I'm very sad for it. But something good came out of it in the end. That was the reason."
I'm not trying to suggest that you run out and start adopting three-legged dogs, but I know it helps me to try and channel that unhappiness into something positive.
I'm not particularly religious, but I do believe in karma. Convert the bad and sad energy into good energy, and the world can only be a happier place.