I hate it when someone says something like "Have a good day" and I get stuck on saying "you too!" and I seem like a complete asshole

I hate it when someone says something like "Have a good day" and I get stuck on saying "you too!" and I seem like a complete asshole It happened today. And thanks to my social anxiety I really do think that he thought I was a complete ass for not saying "you too". I prefer to be quiet and not move my mouth until I can say the word. So if I don't get it out in time it's like I'm not trying to say anything.