I had to activate 3 boosts for my daily challenge yesterday. I did a supply boost earlier in the day and then was supposed to do a 15 minute boost for one extra turn in GE. I clicked on the supply boost again by accident, which I was going to select AFTER my GE boost. I immediately wanted to cancel it without using it in any way. The supply boost was for 4 hours which went a half hour past my daily challenge clock so I was unable to complete it. I think you should have the option to cancel if you haven't used it at all and I knew as soon as I clicked on it I had made the mistake, so I would have cancelled it within seconds. I didn't even care if I got my tavern silver back. If cancelled, delete the required boosts on the quest from 2 back to 1.