If a group coaching course had only 14 days to prove results, the one change that would show it's working is consistent daily action taken by participants on the core habit taught. Instead of just attendance or watching lessons, we'd track whether people actually complete small assigned tasks every day without skipping. This would include check-ins, practice reports, or real-life application evidence tied to each session's goal. If engagement rises and behaviors shift within two weeks, it proves the coaching is not just informative but effective.