I was on disability for six months for depression and migraines. I found that the best thing to do was to be totally honest, especially about how you are feeling and what you are doing. For example, when I first stopped working I felt hopeless, couldn't cope, barely got out of bed each day, had a headache each day, was not a nice person to live with, stopped visiting friends, had gained weight, etc. If you're really nervous, that's okay. It's not a job interview, it's convincing them that you are justifiably sick and your nervousness is part of your illness. If you start to cry, that's okay too.
I would sometimes feel like I was being persecuted because I was "required" to do so much. It was a full time job being on disability but I did a little each day and worked with my psychologist and doctor who were great.
Try not to worry. I did at first and realized it just put me further back in my recovery.