Well, there were two best friends. One got diagnosed with a mental illness. At first, the other friend was very supportive. But as time went on, the friend with the mental illness had some really bad days where she lashed out at her best friend. The healthy friend couldn't handle it after a while and slowly distanced herself. This led to the friend with the mental illness feeling even more alone and abandoned, which was heartbreaking for both of them in different ways.
Sure. There was a pair of best friends. One of them got seriously ill, like with a terminal disease. The healthy friend tried to be there all the time, but as the illness progressed, the ill friend started to push the other away. He didn't want his friend to see him in such a weak state. Eventually, the ill friend passed away, and the remaining friend was left with so much pain and regret, feeling like he could have done more even though he had done so much already.