When a Journey is saved as Live, qualifying contacts start entering the journey. If for some reason, you want to stop any in-progress contacts from finishing that journey, you can click the "Stop" button at the bottom left of the journey canvas.
Clicking stop will launch the below confirmation modal. Once you confirm you want to stop the journey, it will cause in-progress contacts (including those already in delay nodes) to exit the journey, and turn the journey to draft to prevent new entrants.
While it typically only takes a minute to fully stop a given journey, we recommend waiting 5 minutes before turning the journey live again, should you want to allow new entrances.
The live journey stats will update with the count of stopped contacts every 15 seconds, and the in progress counts will go to 0. That's how you know when all contacts have been stopped.
When you delete a journey, that will also stop current in progress contacts to exit the journey, but it means you can no longer set that journey back to live later, and you will have lost any record of the previous stats associated with that journey.