Definitely not the only one! In fact, the first two times I think, I just accepted the money while responding that gosh I uh totally didn't realize I overpaid and slunk off because I am a sad awkward turtle. I didn't even understand why, it's not like I did something bad and yet I felt so embarrassed.
But I managed to push through the next couple of times and while I still have hiccups, it's easier shove tips at people.