PIP review Home assessment

I have my f2f assessment tomorrow, it says at home. I didn't request one but I'm pleased as it makes this so much easier for me.
I had to cancel my previous f2f date due to having chemo same day.
Will the fact I previously cancelled effect me?
I am really nervous and feel panicky my heart is racing just knowing someone is coming. It's so bad I want to cancel but I know I can't!
It's stopping me from trying to prepare, I am worried they will get me to do stuff that is uncomfortable for me.
Also I have my macmillian nurse writing me a support letter as I recently fell down the stairs since I filled the form in, as things are worse. Was there any point in doing this? She often speaks to me on the phone as it's far to my treatment and she knows me well as I been in this treatment a while.
I read somewhere there's no point having a proffesional support letter?

Thanks xx

Thank you.

Just out of curiosity how come I had a home assessment without asking? Is it random or is it because the evidence I've given them is enough for them to warrant one?

I'm hoping it's a good thing as I can't go through the process of a MR or tribunal I don't think I'll have the fight in me!

Thanks x