Hi Seamus, one week ago I was exactly in your situation - I also was quitting again after having support from this site last year.
Leading up to my quit (21st June), I was incredibly nervous - much more so than ever before, and had a really disturbed night on the night before my quit...however, I have done it and so will you.
I wonder if the increased nervousness is a sign that this time it's gonna be forever? I think that might just be the case!!
Anyway, welcome back!!