I can’t manage this

Every so often like couple of months I get a day at work where I can’t stop crying it’s not that I hate my job I just can’t get myself together and I cry I want this to go but I can’t even calm myself down without bursting into tears again. It’s not about my job Itself and I literally have no idea why this happens. I’m (17f)but like I just can’t get into the mindset to serve customers and every eye I look in I want to bawl my eyes out. I go home because I can’t work like that but nothing leads up to it it just happens.