Some days just aren't as good as others. It is important to understand how your body is acting and reacting to different events and happenings at work.
I had yesterday off work because on Thursday I could hardly speak. The frog in my throat had become a toad. If I had of gone to work I would have been able to accomplish two things -
Get more sick.
Share the sickness germs with others in the office.
I hardly ever take sick leave off. If I do it is for one of two reasons - physical health or mental health. Sometimes the brain gets to overwhelmed and I just know that I can't face the office. So I stay home and work remotely instead.
No one is Superman and everyone needs time off to ensure the body remains in functional order and at maximum capacity. If you're sick - stay home!