So sad

I am so sad, we had a calf that a friend brought us on Wednesday. They found it in the field, not sure who the momma was. We were guessing she was about 2 days old. She was so skinny, we have been bottle feeding her. Had to give her a shot and stuff. Then since yesterday was she breathing harder again and just didn't seem to be doing as well. This morning she got another shot and stuff. When we checked on her she was
still hanging in there. We went out a little while ago to give her another bottle and she was dead. I am so sad. I know there was a good chance she wouldn't make it, but it just makes me feel so bad and keep thinking maybe there was something else I could have done.