I had exactly the same problem. I left it there for three days, worried I would loose all my stuff or corrupt flles, but I had enough yesterday. I stopped CC and decided to find out how to do it on my Mac myself....!
If you click on your "Finder" and go to "Applications".
In there I found a folder called "Utilities" and in there you will find "Disk Utility". (Or you could search your Mac for "Disk Utilities" and save yourself the hassle..)
It will open and on the left hand side you click on your Mackintosh HD. On the right hand side there are four different tabs, "First Aid" "Erase" "RAID" and "Restore".
Click "Erase" and it will give you the option to erase free space.
It took an hour or two and kept me updated the whole time. No need for CC. Job done!