Is normal to feel like a failure because my dog attacked another dog for no reason?

Anonymous

For the longest, my bullmastiff was a sweet girl and I never had this issue before. Last week, she attacked another dog and I managed to pull her away before more damage was done.

I've done everything I could to raise a healthy, sociable girl from the time she was a puppy. I had her for 7 years now. I've taken full responsibility for what happened and I'm willing to help the other dog owner with the vet bills and have my girl retrained. It was indeed my fault for taking her to the park and briefly take off her leash. Since I've assumed she was well behaved and socialized, nothing was going to happen. Wrong.

The other owner is understandably very upset at the moment. Is it normal to really feel like a failure? I feel the same as when your child disappoints you and you feel you've failed as a parent, even though you tried everything. This has never happened before, 1st ever time.

Updates
9 mo
I feel absolutely disappointed, shocked and hurt that this happened. I feel as if I failed her somewhere during her upbringing, that I missed something maybe. I don't know what happened. I'm very worried by now.
Is normal to feel like a failure because my dog attacked another dog for no reason?
3 Opinion