Treat it as a fun new game. It's the only way not to end up with your PC being defenestrated...
I originally signed up for the Windows 10 upgrade, but after trying the final release in a VM and finding the UX to be terrible and reading about the privacy issues, I un-signed-up for it. However, every day in Windows Updates would be an "Upgrade to Windows 10" failed message. I then uninstalled and hide the two updates Microsoft tell you to uninstall and hide (KB2976978 and KB3035583) and after this, it seemed to stop with its Windows 10 nonsense...other than the text that should say "Installing updates..." on the Windows Update screen now says "Installing Windows 10..." even though it isn't.
Then on 12th August, it suddenly started logging "Update to Windows 10 Failed..." again and I once again had several gigs of Windows 10 installation files downloaded (I had previously cleaned this up). Turns out there was another update on 11th August that was an update to Windows Update that re-enabled it (KB3075853). So it looks like this is going to keep happening every time there is an update to Windows Update. This is SHIT.
I did an awful lot of Googling but found nothing.
Then I noticed that a new setting had appeared in Group Policy (I have Windows 8.1 Pro, not on a domain, so in gpedit.msc) under Computer Configuration->Administrative Templates->Windows Components->Windows Update called "Turn off the upgrade to the latest version of Windows through Windows Update". Since enabling this policy (I haven't uninstalled the above update), I have not been bothered by Windows 10...until Microsoft find a new way to piss us all off.
I'm completely happy with Windows 8.1 with ClassicShell configured to disable everything TIFKAM-related. It's like running Windows 7, just a bit faster - it's only very very rarely that I see anything that tells me I'm on Windows 8. Windows 10 at the moment is simply not ready for market. I'll have another look at it when it is - and hopefully by then Microsoft will have been forced to back off on some of the privacy idiocies.