My patient died

A couple of weeks ago I had a patient in respiratory distress that went bad very quickly. Looking back, I still feel bad about it and of course wonder if there was something more I could have done for her. I can't give many details of course, but I'm just trying to learn from it and deal with it mentally as best I can. I was in her room a lot after she was admitted to our med surg floor and she didn't seem to be in distress. I had 4 other patients and was going from room to room dealing with each patient and there didn't seem to be anything emergent going on with her. She had visitors, ate lunch, and was on oxygen. She eventually coded and was unable to be revived. She is a coroner case because she was a patient less than 24 hours. Legally, I feel nervous, but I also feel very bad for her family. I know there wasn't any one thing that I failed to do that could've prevented her from dying. She appeared to have a history of poor health. How do other nurses deal with this? And also, is there anything legally I should be aware of? I thought I was a good nurse, but this has thrown me a curve.