Working Retail Is Hard...

I've been working at the local mall for about six months now. Every day feels like it's just one long, unending cycle of trying to keep up with customer demands and inventory changes while also pretending to be cheerful all the time. Today was particularly tough; a customer accused me of overcharging them by mistake when I actually scanned everything correctly... It felt like everyone is rushing past me without ever really seeing or caring about how much work we retail employees do for so little appreciation or acknowledgment. Plus, my manager isn't exactly known for being understanding either... Do others feel this way too? Is it just normal to be tired of smiling and nodding all day long?