Why do I feel so guilty because I had to call sick at work? Is it normal? I’ve been working there for a year, I feel guilty because I told her

I feel guilty because yesterday I told my manager I was getting better and today I’d definitely be able to go. She counted on me, because a lot of people are on holidays. I wasn’t really expecting that I’d get worse, as I was getting much much better. But this morning, I could barely get up, my whole body is sore and very sensitive. My throat is very sore, and I’ve no energy. I have a mild fever as well, not too bad, but enough to make me feel nauseous. I texted her that I’ve gotten worse. She still didn’t answer my message. I’m always ready to work, it’s been a year and they don’t have anything to say about the job that I do. Even though, why am I feeling guilty? I shouldn’t, right?