I feel sad

I just want to ventilate out my feeling I had today postcall.
I feel like I have not done enough for a patient of mine in the ward. I should have acted promptly. I am not sure if I did a correct thing in management, but I knew I miss something in which I could have picked up early.

I see my patient left the way silently. I've been asking myself, was that my fault. I could remember she still nodding reassure me she was 'ok' despite I knew she wasnt and in lots of pain. I feel so bad. I could have save here life, couldnt I?

Just feel sore and remaind in shock after she left so quickly. I dont know what to do.