Every Journey run starts on a new container with a blank slate. Cookies from your application can affect training the Journey, causing a mismatch with the test environment. To best remedy this you can delete just the cookies for your app. Here's how to do that without loosing all of your other browsing data or getting logged out of your favorite apps.
Start by clicking on the three dots menu in the top right of Chrome. Then click Settings > Advanced Settings > Content Settings > Cookies > See all cookie and site data. Or, you can just copy and paste this link into your Chrome URL bar:
Search for your domain name, then select and delete the cookies associated with that site.
Once those are deleted, you can start training or editing your Journey without previous data causing interference.