How do I cope after my dog was put down due to aggression?

I must clarify this dog belonged to my brother and his girlfriend. It was their decision and I disagree with it. I am 20 years old and well aware of the circumstances surrounding their choice. But it was not what I would have done.

Zara was a mix of a collie and labrador. Absolutely lovely dog and always made my day. However, she was always afraid of people. As a pup she used to back away from them. But as she got older she began barking and then lunging. After she tried to bite a friend of my brother’s, my family discussed it and decided it was the safest thing to do as there are many children in the area and it is impossible to keep an eye on her at all times. I was told yesterday evening about the decision and 24 hours later she is gone. I said my goodbyes and I am thankful for that. However, I became so close to the dog I feel quite empty inside knowing that she is gone. I feel I have let her down.
As I have said the decision was not mine and I disagreed with it. I know the reasons behind the decision were valid. I just can’t cope with the fact she is gone. Is there any way to cope with this? Thank you
Also to clarify she has lunged at several people before we have intervened. It was only a matter of time before it happened when nobody was around.
We took her to several behaviour specialists and classes. Nothing was working. This was recommended to us by the local vet.

How can I let three dogs loose in a house?

My family has three dogs, a pitbull, a dalmatian, and a border-collie/german shepherd mix. We are forced to chain them up because our pitbull has almost killed the dalmatian countless times.
how can we let them loose without them trying to fight?

what puppy is a suggestion that would make a good pet and watch dog?

if a collie,sheltie,or border collie doesn’t make a good dog for kids then what dog does?they really want a puppy.

Where can a nervous female dog be taken to be rescued from the Mercer County Animal Shelter?

There is a large female dog that I think has been badly abused and now she is afraid of everything. She looks like a boxer/rotweiller mix I think. Can anyone help or give ideas to save this dog’s life from being put to sleep. It would take someone experienced in handling dogs like this because she is unpredictable now because she is afraid of everything.

What breed of dog would be best for apartment living and owner with busy schedule?

I live alone in a spacious apartment with a cat. I’d like to get a small dog. I work about 8-9 hours a day. My dog, like my cat, would have my undivided attention when I am home, but is this situation a bad one for the quality of a dog’s life?

How do you deal with losing your dog?

My dog is still living, but I am sad to say that she is already 14. She is so very healthy at this age, which is good, I am grateful to have such a healthy dog at such a old age. But, I know that a dog’s life can go downhill fast, and I am scared knowing that she may only have a couple of years left…I dred the day that I will have to say goodbye to her. I don’t want that to happen but I know it will and I don’t know how to deal with it.
She has been my best friend since I was 6 years old and I’ve loved her more than I love myself. Losing her will be like losing everything I have ever known.
How does one cope with losing your best friend? One that’s never judged you and loved you no matter how much the rest of the world hated you? This may be years from now, or it may be in the next few months, but whenever the time comes, I want to know how to deal with it.
Someone with experience in this.
My dad, who lost his dog when he was 15 still cries when he thinks about her. And he never cries, he is also 59. The fact that a tiny animal can carry a persons love after they are gone amazes me.
How can I possibly deal with this when it happens?
Thank you.