I was treated cruelly by a stranger. How do I get over it?

I am a housekeeper, and yesterday I got scammed by a customer. Because I did not take the necessary steps to protect myself (I was supposed to bring a checklist but didn’t), he got away with the scam, and I ended up doing 3 hours of work for free, cleaning a shithole apartment shared by 4 shithead Trump-supporting frat boys. They made up total lies, like saying that I left early and that I didn’t do anything while I was there, and demanded a total refund, which my employer granted, because I didn’t have the checklist to back myself up. I basically got robbed. I’m no longer with this employer.

I acknowledge I fucked up, but how do I get over this now? I was so hurt. I am a former self-harmer, and I relapsed yesterday. I am still upset.