Is it mean or selfish of me to be upset?

Why dont you just say no?

It’s not mean or selfish for you to be upset, it’s just a little pointless. The reason your sister waited the last minute to ask, and gave her kids all the sugar, is because she knew you might be upset, and you may or may not say anything, but at the end of the day you will still baby sit for her, and you’ll do it again next time. Even if she asks last minute and feeds her kids sugar. So you can be as upset as you want, but it isnt going to accomplish anything. Next time, lay down the law. Say no. Tell her you will not baby sit for her without advance notice, and when the kids are in your house, they will eat what you provide. She can be upset, and call you mean, and I’m guessing this comes from your family as well? But that’s ok. Apparently they’ve been treating you like a doormat for long enough. Time to stand up for yourself already. And that is NOT meanness. It isnt selfishness. it is simply saying I am a worthwhile person. I deserve to be treated with respect and consideration. If you do not treat me with respect and consideration, I will not do things for you. Or you can continue being upset.