If you decide you want to get rid of a SmartPath that you've already launched, you can undo it. Undoing a SmarPath will remove all scheduled tasks associated with that specific SmartPath. Undoing will of course not affect tasks that have already been completed.
Navigate to Sales Campaigns in the left sidebar, then click SmartPaths.
Find the SmartPath that you want to undo, and click on the action pencil on the right side.
Click "Undo SmartPath" in the drop-down menu.
On the SmartPath Assignments page, you'll see every launch of that SmartPath. So, if you've launched it multiple times at different dates and times, then be sure you select the correct instance of the SmartPath. Click on the action pencil on the right side. From the Action drop-down menu click "Undo SmartPaths".
An Undo SmartPath Assignments window will appear. Click the checkbox to confirm undoing the SmartPath. Click the Undo Assignment button to actually undo.
All tasks associated with the SmartPath will now be removed.