The Sibling Sabotage

I did something really petty recently, and I'm trying to figure out why. Last week, my older sister asked me to water her plants while she was away at a friend's birthday party for the weekend. She specifically said, 'Don't forget, it'll dry them up in this heat.' So of course, I forgot. On purpose. Every day, I'd see the watering can sitting next to the sink and think about how easy it would be just to do it. But every time, I'd walk away with a smirk. It wasn't that she was mean or anything, we get along fine, mostly leave each other alone. So why did I feel this inexplicable need to sabotage her? Maybe because it's been hard watching my sister excel in everything while I struggle just to keep up. Or maybe it’s pure sibling rivalry. Either way, when she got back and found her plants withering on the windowsill, she looked really upset for a second before turning around and telling me exactly what she thought of my stunt without raising her voice once. I felt terrible afterward but didn't know how to apologize properly. Maybe next time I’ll be better.