Sounding chipper as all hell goes a looooong way. That and I tend to let them have the mistake too if it was my mistake. If it was their mistake than nah, I'm dumping it unless another barista wants it cuz otherwise you get scammers. Most folks are way more chill about remake time when you're like "oh! We'll go ahead and take this one too, make someone's day with it!"

You shouldn’t feel disappointed! You are still learning! What I liked to do “and still do on occasion if I feel a little out of it” is say I’m still new and learning sorry about that. 99 percent of the time the customer will calm down and be like ohhh okay it’s no problem and it’ll calm you down a little and you can focus on practicing! You’re only human after all in time you will get better don’t give up!