How do I stop a journey when a customer starts a different campaign?

You can make journeys mutually exclusive so that entering a higher-priority campaign removes the user from a lower-priority one. There are two mechanisms; pick the one that matches how you want the exit reported in statistics.

Option 1: Exit conditions (recommended for prioritization)

Exit conditions remove users from a journey as soon as the condition is met, and they are not counted as conversions. Use this when leaving the journey is not a success for that campaign - for example, the user qualified for a different campaign.

1. Identify the event that starts the high-priority journey (for example win_back_start).
2. Open the settings of the journey you want to stop.
3. Add that event as an exit condition.

Option 2: Conversion goal

If reaching the other campaign genuinely is the success metric of the first journey, set the event as a conversion goal instead and enable End journey after this event. Messages that have not been sent by the time the goal is reached will not be sent.

Be aware that this counts every exit as a conversion, which inflates the conversion rate of the journey you are stopping - which is why exit conditions are the better fit for pure prioritization.

With either option, when the win_back_start event fires the user moves into the new campaign and their progress in the previous one ends at the same time.