Sorry about the job, don't be too hard on yourself. I'm signed off work at the moment because of depression. I've had my job for ten years and without wanting to boast I'm one of the most experienced in my line of work in Britain. Yet despite that, I was overwhelmed and simply couldn't cope with the most straightforward of tasks that were well below my level of responsibility. I kept screwing up things I had done many times before and my concentration was shot. So it wasn't you, it was the depression and eventually you will be well enough to give things another go.