One of those days

7 hours in to my 8 hour workday and I've maybe been productive for 2 hours at most. Every little challenge is too much for me today. I feel so overwhelmed and hopeless. Some days I can roll with the punches and still smile, other days I can't function at all. Nothing particularly bad has happened today, I've tried being positive and being productive and trying to concentrate. I've written out a plan and I've spoken to a listener. I felt more reassured after that but my anxieties just came back. The worst part will be that at some point I will feel like I 'wake up' and this big horrible bubble of pressure will suddenly be gone for another day. On my good days I keep telling myself it's getting better and deep down I know it is. But on these bad days I just feel so useless and hate how little control I have. I then panic more because I know I'm being a bad friend, a bad employee and just a useless person all up really. I want to hide from it all but that won't fix anything. What do you do on these days?