Anxiety attacks at work

Anyone else have anxiety problems like me? I've had them all my life and I grew up very timid and shy up to my college years.

Currently I'm working retail, and I'm having issues with dealing with my anxiety when I have to deal with really troubling customers to a point I have angry crying moments because I can't say anything back if the customer started being rude to me. I tried breathing exercises and counting in my head but nothing seems to help me. I can't walk it off like I want to because I'm a cashier. I usually have to stand in one area unless my boss tells me to work someplace else.

Does anyone have any anxiety tips to share? This has happened to me a couple times and I really don't want moments like this to happen because I'm scared I'll be fired or let go because of it.

Thanks in advance.