Why Did I Do That to the Manager?...

So there's this customer, let's call him Bob. He comes in every week to buy lottery tickets and always gets these long, drawn-out conversations with my manager. I mean, it's not that I hate talking to customers... but with Bob, he's got a whole backstory about why he needs to win the lottery, like it's going to solve all his problems and fix his life in one big swoop... It just drives me nuts because I know none of that stuff is true. My manager listens so intently, nods along... And every time Bob leaves, she looks at me with these wide eyes and says, 'You won't believe what he said this week!' and starts telling me his story again, as if I wasn’t there for it in the first place. Last Tuesday was particularly grueling. We were short-staffed and had a rush of customers coming through because of a sale. Bob showed up and just started going on and on... My manager kept her usual smile, nodding and saying all the right things to keep him talking. But I felt myself losing it, like any moment I was going to explode or something. Right as we were running out of time to meet the deadline for our delivery orders, Bob's rambling finally hit a nerve with me. I mean, it's not his fault... It's just that my manager seemed to be missing an important order while she was busy with this endless chat with him... So in a moment of... well, let's call it frustration, I kind of... blurted out something really unprofessional and rude about Bob. The look on my manager’s face when the words left my mouth was priceless. She went from being all sunshine and smiles to this deep frown, her eyes narrowing in shock. It felt like time slowed down as she processed what I had just said... Then it got really quiet after that. I could see other employees looking at us with wide eyes, wondering if they should intervene or not. In the end, my manager took me aside later and we talked about professionalism and customer service. She was surprisingly understanding given how out of line I went... But she made sure to emphasize the importance of staying calm under pressure. So here's where it gets tricky for me: did I actually cross a line? Or was there something in my actions that could have been better handled with more tact? And what does this mean for my career at this store if it happens again?...