Caught a calculation error

I’ve written a draft of my first chapter and had all my stats finalized. I went back and checked something today and noticed a calculation didn’t make sense. Flash forward 6 hours and here I am redoing half my stats which will then alter my results and parts of my discussion. I know it’s nothing to be ashamed or embarrassed about but I just cannot believe I didn’t catch this mistake. I’m so glad I caught it now when I’m in the early stages of writing but I’m still so frustrated. Pls tell me you’ve experienced this before so I don’t feel like such an idiot