i did something mean to my sister

so last weekend i was really stressed out over work stuff and just had one of those days where everything feels like it's going wrong. my parents were away for the weekend, so i was home with my little sister who is always asking for help or attention and yeah, i snapped at her when she came into my room to ask what we're having for dinner. i told her off pretty harshly and then just locked myself in my room with a book, ignoring her even though i could hear her crying outside the door. it's not like me to be so mean but afterwards, i felt really bad about it, kept replaying how she was looking at me when i yelled. now every time i see her or think about that day, i feel guilty and wish i could take it back.