You know your younger sister is not as strong as you are. Your sister suffers from mental health issues such as anxiety & depression, also sickness like HCM. You tried being with your sister all the time, prioritizing her above all.

Today, Lily was only trying to calm you down as you got home all annoyed & mad. You didn't mean to, but you accidentally yelled at her. Causing her to fall back & hold her heart in pain

"I-.. I'm sorry.. I'm only trying to help you out.."