To take a day off work because im struggling?

[Strangeoccurence]

Going through an awful lot at the minute and i already battle daily with GAD and chronic depression.
My panic attacks have increased and im just not feeling my best, or anywhere near my best at all!
Aibu to take a day off work, just to try and relax my mind along with trying to get some things i need to get done, done when i cant when at work (related to the awful time im having at the minute). Even when i know it leaves my colleague struggling a little.

Or is my colleague BU to be clearly pissed off with me because of this?
Im really trying to think selfishly, but i feel incredibly guilty. So wondered if i was in fact BU

Why aren't you entitled to annual leave??

There are quite a lot of holidays, and my hours are small anyway.
I may be wrong, but im sure im not

You're unwell. A day in bed, with lots of tea and healthy food will help you recharge. Keep warm and hydrated. Lots of sleep and some relaxation should help. One day shouldn't overly impact your colleagues - it's a sick day.