> When you cancel it, previously downloaded html and
> related files are not part of the current mirror.
> Httrack then deletes them (options -> Build -> Do
> not purge=unchecked)

So should I just check this option? 

> Stop canceling it. Just Mirror -> Pause.

If I pause it I'm not able to exit the program and continue two days later,
right? Then this is not quite feasible for me.