I'm wondering if anyone else reacts the same way that I do to even good news and pleasant surprises?

I've just been offered a job that it perfect for me and which I didn't expect to get. So why is it that my mood changed instantly from euphoria to panic and anxiety? At the moment my stomach is churning, acid is burning and I have aches and pains in my arms and my neck is achingly stiff and I feel like I can't breathe....... (althugh admittedly I have been feeling like this for a couple of days due to pre-interview anxiety).

Anyone else experienced similar or am I just a confirmed neurotic!!!