Anyone find it hard to say thank you?

Anyone find it hard to say thank you? I swear every single time I know I’m gonna have to say thank you I stutter (for example: you paid the cashier at the market and as your preparing to leave you know your gonna say thank you) and today I was in that situation and I embarrassed myself by going t-t-d-d-t-thank you. It’s so frustrating and embarrassing