Running during the day (and with sunshine) was really nice.
Not doing it after a whole day at work (which is often exhausting in itself).
Brilliant advice from A. He told me to that I could run the whole 8 miles and that I just needed to believe in myself and keep going.
Taking it slow and steady (more advice from A).
All things considered, the biggest difference was my mentality in approaching the run. And I almost enjoyed it; I'm definitely proud that I did it - 8 miles under the belt is a better position to be in, preparing for my upcoming event. (I daren't use the word "race" as I will be in no way racing!)
Am going to let my legs recover a bit (especially my left knee, which seems to be rebelling slightly) and then maybe go for a stamina-building but non-impact swim...