I see a lot of folks going back and forth with their manager about trying to call in. It would be amazing if your employer cared about you, but they’re busy trying to get promoted or not fired. They don’t care. They will argue with you because it benefits them; don’t let them. “Sorry, I have plans, can’t cover that shift.” Then, if they keep texting, “how do you want me to record this time on my timesheet?” If you aren’t coming in for a scheduled shift, “I can’t make it in, I’m sorry. I did x and y to get my shift covered. Good luck!” If they push, “I’m not sharing medical information with you.” Don’t let them know your mental state, don’t tell them you need a mental health day, or someone died, or you’re crying. Just keep it dry and boring and they’ll give up when they can’t get purchase. Use the Grey Rock Method like you would with an abusive family member.
I also see a lot of people saying “they know my availability!” Or “I asked people to cover the shift, so they should know I’m not coming in!” Writing a schedule is a huge pain in the ass, and it’s very hard to remember everyone’s commitments. Totally valid to remind them and to not violate that boundary, but don’t take it personally, it’s not personal. And as for trying to get coverage, that could mean you have other optional plans, so if you don’t explicitly tell the manager who will be on duty during your shift, you need to do that. They might not even have known you were looking for coverage. Always call in first, find coverage second.
You don’t have to do any of this, but keeping an emotional distance from work is about the only way to survive long term in a shitty job.