Today's Mix-Up at the Cafe

So today, I had this huge mix-up with an order. It was this nice lady who always orders a grande vanilla latte, but that day she asked for something different and I got super confused. Instead of writing it down like normal, I just went ahead and made what I thought she wanted based on her usual order. But when I brought out the drink, she looked at me all surprised and said, 'Is this a regular vanilla latte?' It was pretty clear right then that I messed up big time. She seemed a bit disappointed but tried to be nice about it. Now I'm overthinking everything, did she really just want her usual? Did she think the latte looked too small? Am I doing my job poorly now because of this mistake? Sometimes, these little things get stuck in your head for days.